polymers are pervasive 
 throughout all aspects of the modern age 
 and , as described by rolf mlhaupt ,  without polymers , 
 modern life would be impossible because polymers secure the high quality 
 of life and serve as pacemakers for modern technologies  . consequently , the urge to find renewable resources 
 to reduce consumption of fossil fuel feedstocks , decrease the use 
 of energy intensive products , and solve recycling and/or degradation 
 issues has led to the investigation of biopolymers .
additionally , 
 the increase in fuel costs observed over the past 30 years dictates a transition to polymeric precursors 
 that do not rely expressly on fossil fuels .
however , the full life 
 cycle assessment of most bio - based polymers is not well reported , 
 and a focus on the environmental impacts of biopolymers will be necessary . as unrecycled polymers end up in the oceans ( estimated 
 5 billion kg per year ) , water - degradable 
 polymers such as polycarbonates that degrade into carbon dioxide and 
 diols represent a reasonable class of 
 materials to investigate further .
polycarbonates are mainly 
 used where toughness , high optical transparency , 
 and solvent resistance are required .
although more stable toward hydrolysis 
 than their polyester counterparts , polycarbonates are able to degrade 
 in water and are , thus , considered as aqueous degradable materials .
strategies for the use of renewables in polycarbonates 
 include polycondensation of feedstock products such as aliphatic diols , ring - opening polymerization of 6-membered cyclic 
 carbonates , epoxides and carbon dioxide - based 
 systems , polycondensation of cereal - based products 
 such as 1,4:3,6-isosorbide , and natural 
 phenols to afford copolymers .
noteworthy , 
 biorenewable - based polycarbonates have found applications as powder 
 coating agents and as drug delivery vehicles .
previous efforts from our lab have led to the synthesis of polycarbonates 
 derived from both carbohydrates and quinic 
 acid . in an effort to broaden the scope 
 to natural products with biological activities ,
amide)s 
 derived from rather inexpensive ferulic acid and a hydroxyl - amino 
 acid .
it was hypothesized that bio - based poly(carbonate  amide)s 
 derived from fa and a hydroxyl - containing amino acid would possess 
 interesting mechanical properties arising from the rigid conjugated 
 cinnamic acid core of fa and the h - bonding potential of the amino 
 acid component , while also having the potential to undergo hydrolytic 
 breakdown and lead to biologically beneficial byproducts and carbon 
 dioxide .
ferulic acid ( 4-hydroxy-3-methoxycinnamic acid , fa ) is a 
 secondary metabolite of the biosynthesis of lignin , derived from phenylalanine 
 and tyrosine via shikimate pathway .
0.3 wt % in wheat bran ) , fruits , vegetables , 
 and plant tissues .
fa can be naturally found in its free form , as 
 monomers , dimers , or polymers but also as esters formed by condensation 
 with hydroxyl acids , alcohols , or saccharides or as amides formed 
 by condensation with amines . because of its antioxidant properties , 
 fa exhibits a wide range of therapeutic effects such as anticancer , 
 antidiabetic , cardio - protective , neuro - protective , and anti - inflammatory 
 activities .
it has also found use as a food preservative and has shown antibacterial activity against 
 gram - negative and -positive bacteria , including the anthrax agent b. subtilis .
moreover , fa has 
 been incorporated into a biodegradable polymer as a pendant group 
 to enhance antioxidant properties , specifically for tissue engineering 
 applications .
 ester ) , poly(ether 
 ester)s , a methacrylic  fa copolymer , and a polyamide . to the best of our knowledge ,
all chemicals and reagents were used as received 
 from sigma - aldrich co or vwr international .
caution : special precautions should be taken when working with phosgene 
 precursors , including diphosgene and triphosgene .
they are highly 
 toxic by inhalation and ingestion ; use of personal protective equipment , 
 including a respiratory mask , is recommended .
tetrahydrofuran ( thf ) 
 and dichloromethane were purified by passage through solvent purification 
 system ( jc meyer solvent systems ) and used as dried solvents .
column 
 chromatography was performed on a combiflash rf4x ( teledyne isco ) 
 with redisep rf column ( teledyne isco ) .
ir spectra 
 were recorded on a shimadzu ir prestige attenuated total reflectance 
 fourier - transform infrared spectrometer ( atr - ftir ) and analyzed using 
 irsolution v. 1.40 software .
size exclusion chromatography ( sec ) measurements 
 were performed on a waters chromatography inc .
( milford , ma ) system 
 equipped with an isocratic pump model 1515 , a differential refractometer 
 model 2414 , and a four - column set of 5 m guard ( 50  7.5 
 mm ) , styragel hr 4 5 m dmf ( 300  7.5 mm ) , styragel hr 
 4e 5 m dmf ( 300  7.5 mm ) , and styragel hr 2 5 m 
 dmf ( 300  7.5 mm ) using dmf ( 0.05 m libr ) as the eluent ( 1.00 
 ml / min ) at 70 c .
polymer solutions were prepared at a concentration 
 of about 5 mg / ml and an injection volume of 200 l was used . 

data collection and analysis were performed with empower 2 v. 6.10.01.00 
 software ( waters , inc . ) .
the system was calibrated with poly(ethylene 
 oxide ) standards ( polymer laboratories , amherst , ma ) ranging from 
 106 to 174  000 da , and an additional internal calibration based 
 on the oligomeric fraction was also realized ( supporting information , methods to monitor the polymerizations ) . 

glass transition temperatures ( tg ) and 
 melting points ( mp ) were measured by differential scanning 
 calorimetry ( dsc ) on a mettler - toledo dsc822 ( mettler - toledo , inc . , 

measurements of tg were recorded with a heating rate of 15 c / min , 
 and those for mp were recorded with a 
 heating rate of 10 c / min .
thermogravimetric analysis 
 ( tga ) was performed under an ar atmosphere using a mettler - toledo 
 model tga / dsc 1 , with a heating rate of 10 c / min .
all steady - state emission , excitation , and 3 d spectra were obtained 
 with a horiba fluoromax4 with automatic polarizers .
measurements were 
 performed in dmf in matched quartz cuvettes with path lenghts of 1 
 cm . to a solution of tyrosine 
 ethyl ester hydrochloride ( 1.57 g , 6.39 mmol ) in ch2cl2 ( 23 ml ) were added ferulic acid ( 1.97 g , 6.39 mmol ) and hobt 
 ( 863.3 mg , 6.39 mmol ) .
the reaction was cooled down at 0 c , 
 and et3n ( 2.7 ml , 19.17 mmol ) and edci ( 992 mg , 6.39 mmol ) 
 were added .
was added a saturated aqueous solution of nahco3 , and the crude product was extracted with ch2cl2 , dried over na2so4 , and filtered .
the 
 solvent was removed , and the crude product was purified by flash chromatography 
 0% to 100% of acoet in hexane over 40 min ( 80 g silica cartridge ) . 
 the solvent was removed to give the desired product as a white foam 
 ( 1.65 g , 4.28 mmol , 67% ) .
ftir ( atr ) max ( cm ) : 36003150 , 1726 , 1667 , 1514 .
h nmr spectrum ( 500 mhz , cdcl3 )  : 7.54 ( d , j = 15.5 hz , 1 h ) , 7.28 ( d , j = 0.9 hz , 
 1 h ) , 7.046.93 ( m , 4 h ) , 6.89 ( dd , j = 8.1 , 
 0.9 hz , 1 h ) , 6.786.73 ( m , 2 h ) , 6.296.24 ( m , 2 h ) , 
 6.07 ( br s , 1 h ) , 4.99 ( dtd , j = 6.7 , 5.7 , 1.0 hz , 
 1 h ) , 4.21 ( q , j = 7.2 , 2 h ) , 3.88 ( s , 3 h ) , 3.16 
 ( dd , j = 14.1 , 5.7 hz , 1 h ) , 3.08 ( dd , j = 14.1 , 5.7 hz , 1 h ) , 1.29 ( t , j = 7.2 , 3 h ) ppm .
c nmr spectrum ( 125 mhz , cdcl3 )  : 172.0 
 ( c ) , 166.0 ( c ) , 155.3 ( c ) , 147.6 ( c ) , 146.7 ( c ) , 142.1 ( ch ) , 130.4 
 ( 2 ch ) , 127.3 ( c ) , 127.0 ( c ) , 122.5 ( ch ) , 117.2 ( ch ) , 115.5 ( 2 ch ) , 
 114.7 ( ch ) , 109.6 ( ch ) , 61.7 ( ch2 ) , 55.9 ( ch3 ) , 53.5 ( ch ) , 37.2 ( ch2 ) , 14.2 ( ch3 ) ppm . ms 
 ( esi ) m / z ( % ) 386.2 
 ( 100 , [ m + h ] ) .
esihrms calcd for c21h24no6 ( m+h ) 386.1604 ; found 386.1609 ; mp = 70 c . to a solution of l - tyrosine ethyl ester chlorohydrate 
 ( 5.4 g , 22.0 mmol ) in thf ( 110 ml )
were added dmap ( 536.8 mg , 4.4 
 mmol ) , et3n ( 9.2 ml , 65.9 mmol ) , and tbdmscl ( 8.3 g , 54.9 
 mmol ) .
the reaction was stirred at reflux for 3 h. after cooling down 
 at room temperature , the mixture was filtered and the filtrate was 
 purified by flash chromatography 0% to 100% of acoet in hexane over 
 40 min ( 80 g silica cartridge ) .
the solvent was removed to give the 
 desired product as a colorless oil ( 5.8 g , 17.9 mmol , 81% ) . ftir ( atr ) 
 max ( cm ) 1732 , 1510 .
h nmr spectrum ( 500 mhz , cdcl3 )  : 7.04 ( d , j = 8.4 hz , 2 h ) , 6.76 ( d , j = 8.4 hz , 
 2 h ) , 4.15 ( q , j = 7.1 hz , 2 h ) , 3.66 ( dd , j = 7.7 , 5.5 hz , 1 h ) , 3.00 ( dd , j = 13.7 , 
 5.5 hz , 1 h ) , 2.81 ( dd , j = 13.7 , 7.7 hz , 1 h ) , 1.24 
 ( t , j = 7.1 hz , 3 h ) , 0.97 ( s , 9 h ) , 0.18 ( s , 6 h ) 
 ppm .
c nmr spectrum ( 125 mhz , cdcl3 )  : 
 175.1 ( c ) , 154.5 ( c ) , 130.2 ( 2 ch ) , 129.8 ( c ) , 120.1 ( 2 ch ) , 60.9 
 ( ch2 ) , 55.9 ( ch ) , 40.4 ( ch2 ) , 25.7 ( 3 ch3 ) , 18.2 ( c ) , 14.2 ( ch3 ) , 4.4 ( 2 ch3 ) ppm . ms ( esi ) m / z ( % ) 324.2 ( 100 , [ m + h ] ) .
esihrms calcd for c17h30no3si ( m+h ) 324.1995 ; found 324.2004 . to a solution of 10 ( 5 g , 
 15.5 mmol ) in ch2cl2 ( 77 ml )
were added ferulic 
 acid ( 5 g , 15.5 mmol ) and hobt ( 2.1 g , 15.5 mmol ) .
the reaction was 
 cooled down at 0 c and et3n ( 4.3 ml , 31.0 mmol ) and 
 edci ( 2.4 g , 15.5 mmol ) .
was added a saturated aqueous solution of 
 nahco3 and the crude product was extracted with ch2cl2 , dried over na2so4 , and 
 filtered .
the solvent was removed under vacuum , and the crude product 
 was purified by flash chromatography 0% to 50% of acoet in hexane 
 over 50 min ( 120 g silica cartridge ) .
the solvent was removed to give 
 the desired product as a yellow foam with 10% of 10 ( 6.39 
 g , 12.8 mmol , 83% ) .
ftir ( atr ) max ( cm ) 35003150 , 1732 , 1657 , 1593 .
h nmr spectrum 
 ( 500 mhz , cdcl3 ) h  : 7.53 ( d , j = 15.6 hz , 1 h ) , 7.056.94 ( m , 5 h ) , 6.88 ( d , j = 8.4 hz , 1 h ) , 6.74 ( d , j = 8.4 hz , 
 2 h ) , 6.25 ( d , j = 15.6 hz , 1 h ) , 6.19 ( d , j = 7.8 hz , 1 h ) , 4.96 ( dt , j = 7.8 , 5.7 
 hz , 1 h ) , 4.17 ( qd , j = 7.0 , 1.8 hz , 2 h ) , 3.88 ( s , 
 3 h ) , 3.163.08 ( m , 2 h ) , 1.25 ( t , j = 7.1 
 hz , 3 h ) , 0.96 ( s , 9 h ) , 0.17 ( s , 6 h ) ppm .
c nmr spectrum 
 ( 125 mhz , cdcl3 )  : 171.8 ( c ) , 165.6 ( c ) , 154.6 ( c ) , 
 147.6 ( c ) , 146.8 ( c ) , 141.7 ( ch ) , 130.3 ( 2 ch ) , 128.5 ( c ) , 127.0 ( c ) , 
 122.4 ( ch ) , 120.0 ( 2 ch ) , 117.4 ( ch ) , 114.8 ( ch ) , 109.5 ( ch ) , 61.5 
 ( ch2 ) , 55.8 ( ch3 ) , 53.4 ( ch ) , 37.1 ( ch2 ) , 25.6 ( 3 ch3 ) , 18.1 ( c ) , 14.1 ( ch3 ) , 4.5 
 ( 2 ch3 ) ppm . ms ( esi ) m / z ( % ) 500.2 ( 100 , [ m + h ] ) ; esihrms calcd for 
 c27h38no6si ( m+h ) 500.2468 ; found 
 500.2453 ; mp = 47 c .
a solution of 11 ( 2.07 g , 
 4.14 mmol ) and pyridine ( 3.1 ml , 6.2 mmol ) in ch2cl2 ( 12.5 ml ) was added dropwise to a solution of p - nitrophenyl chloroformate ( 1.69 g , 8.28 mmol ) in ch2cl2 ( 25.1 ml ) .
the reaction was stirred at room temperature for 
 7 h. water was added , and the crude was extracted with ch2cl2 , dried over na2so4 , and filtered . 

the residue was purified by 
 flash chromatography on a silica cartridge ( 80 g , hexane / acoet 0 to 
 50% over 30 min ) .
the desired product was obtained as a yellow foam 
 ( 1.95 g , 2.93 mmol , 71% ) .
h nmr spectrum ( 500 mhz , cdcl3 )  : 8.30 ( d , j = 9.2 hz , 2 h ) , 7.57 
 ( d , j = 15.5 hz , 1 h ) , 7.48 ( d , j = 9.2 hz , 2 h ) , 7.21 ( d , j = 8.7 hz , 1 h ) , 7.157.09 
 ( m , 2 h ) , 6.98 ( d , j = 8.4 hz , 2 h ) , 6.75 ( d , j = 8.4 hz , 2 h ) , 6.37 ( d , j = 15.5 hz , 
 1 h ) , 6.22 ( d , j = 7.8 hz , 1 h ) , 4.96 ( dt , j = 7.8 , 5.6 hz , 1 h ) , 4.19 ( qd , j = 7.1 , 
 2.6 hz , 2 h ) , 3.93 ( s , 3 h ) , 3.213.05 ( m , 2 h ) , 1.27 ( t , j = 7.1 hz , 3 h ) , 0.96 ( s , 9 h ) , 0.17 ( s , 6 h ) ppm .
c nmr spectrum ( 125 mhz , cdcl3 )  : 171.7 
 ( c ) , 164.8 ( c ) , 155.4 ( c ) , 154.7 ( c ) , 151.0 ( c ) , 150.2 ( c ) , 145.5 
 ( c ) , 140.55 ( c ) , 140.50 ( ch ) , 134.5 ( c ) , 130.3 ( 2 ch ) , 128.4 ( c ) , 
 125.4 ( 2 ch ) , 122.3 ( ch ) , 121.6 ( 2 ch ) , 121.0 ( ch ) , 120.8 ( ch ) , 120.1 
 ( 2 ch ) , 111.5 ( ch ) , 61.6 ( ch2 ) , 56.1 ( ch3 ) , 
 53.4 ( ch ) , 37.1 ( ch2 ) , 25.6 ( 3 ch3 ) , 18.1 ( c ) , 
 14.2 ( ch3 ) , 4.5 ( 2 ch3 ) ppm ; ms ( esi ) m / z ( % ) 665.3 ( 100 , [ m 
 + h ] ) .
esihrms calcd for c34h41n2o10si ( m + h ) 665.2530 ; found 665.2519 ; mp = 56 c . to a solution of 12 ( 1.74 g , 2.74 mmol ) in ch2cl2 ( 13.7 
 ml )
the reaction was stirred at room temperature for 23 h. 
 a saturated solution of nahco3 was added , and the crude 
 was extracted with ch2cl2 , dried over na2so4 , and filtered .
the residue was purified by flash chromatography on a silica 
 cartridge ( 120 g , hexane / acoet 0 to 100% over 40 min ) .
the desired 
 product was obtained as a white foam ( 1.28 g , 2.33 mmol , 85% ) .
ftir 
 ( atr ) max ( cm ) 33003150 , 
 1782 , 1732 , 1661 , 1514 .
h nmr spectrum ( 500 mhz , cdcl3 )  : 8.27 ( d , j = 9.2 hz , 2 h ) , 7.52 
 ( d , j = 15.6 hz , 1 h ) , 7.45 ( d , j = 9.2 hz , 2 h ) , 7.15 ( d , j = 8.7 hz , 1 h ) , 7.11 
 ( br s , 1 h ) , 7.037.02 ( m , 2 h ) , 6.95 ( d , j = 8.4 hz , 2 h ) , 6.72 ( d , j = 8.4 hz , 2 h ) , 6.51 
 ( d , j = 7.9 hz , 1 h ) , 6.37 ( d , j = 15.6 hz , 1 h ) , 4.96 ( dt , j = 8.0 , 5.7 hz , 1 h ) , 
 4.234.16 ( m , 2 h ) , 3.86 ( s , 3 h ) , 3.13 ( dd , j = 14.1 , 5.7 hz , 1 h ) , 3.03 ( dd , j = 14.1 , 6.2 hz , 
 1 h ) , 1.26 ( t , j = 7.1 hz , 3 h ) ppm .
c nmr spectrum ( 125 mhz , cdcl3 )  : 171.9 ( c ) , 165.5 
 ( c ) , 155.5 ( c ) , 155.3 ( c ) , 150.9 ( c),150.3 ( c ) , 145.5 ( c ) , 140.9 ( c ) , 
 140.5 ( ch ) , 134.3 ( c ) , 130.3 ( 2 ch ) , 127.0 ( c ) , 125.3 ( 2 ch ) , 122.3 
 ( ch ) , 121.6 ( 2 ch ) , 120.74 ( ch ) , 120.67 ( ch ) , 115.5 ( 2 ch ) , 111.6 
 ( ch ) , 61.8 ( ch2 ) , 56.0 ( ch3 ) , 53.7 ( ch ) , 37.0 
 ( ch2 ) , 14.1 ( ch3 ) ppm . ms ( esi ) m / z ( % ) 551.2 ( 100 , [ m + h ] ) . esihrms calcd for c28h27n2o10 ( m + h ) 551.1666 ; found 551.1654 . to a solution of 13 ( 702 mg , 1.27 mmol ) in 
 pyridine ( 0.42 ml ) was added dropwise triethylamine ( 0.36 ml , 2.55 
 mmol ) .
the mixture was stirred at room temperature for 5 h and was 
 quenched with a saturated solution of nahco3 .
the product 
 was extracted with ch2cl2 and dried over na2so4 , and the solvent was removed .
the mixture was 
 solubilized in ch2cl2 , precipitated into meoh 
 three times , and dried under vacuum to give the desired product as 
 a yellowish solid which follows aaaa , aaaa , 
 aaaa patterns in 22/15/63 proportions ( 389.5 mg , 0.94 
 mmol , 74% ) .
ftir ( atr ) max ( cm ) 34003200 , 1778 , 1736 , 1661 , 1624 , 1508 .
h nmr 
 spectrum ( 500 mhz , cdcl3 )  : 7.617.51 ( m , 
 14 h ) , 7.237.20 ( m , 98 h ) , 6.436.23 ( m , 28 h ) , 5.00 
 ( br s , 14 h ) , 4.234.14 ( m , 28 h ) , 3.87 ( br s , 42 h ) , 3.273.13 
 ( m , 28 h ) , 1.321.10 ( m , 42 h ) ppm .
c nmr spectrum 
 ( 125 mhz , cdcl3 )  : 171.5 ( 14 c ) , 165.1 ( 14 c ) , 152.0 
 ( 3.1 c(o)aaaa ) , 151.3 ( 8.8 caaaa ) , 151.22 ( 5.2 caaaa ) , 151.16 ( 8.8 c(o)aaaa ) , 150.7 ( 2.1 c(o)aaaa ) , 150.2 ( 8.8 caaaa ) , 150.0 ( 5.2 caaaa ) 141.1 , 141.0 , 140.9 ( 14 ch + 14 c ) , 134.2 , 
 134.1 , 134.0 ( 28 c ) , 130.52 , 130.49 ( 28 ch ) , 122.6 ( 8.8 chaaaa ) , 122.5 ( 5.2 chaaaa ) , 120.94 , 120.89 , 
 120.8 ( 28 ch ) , 120.6 ( 14 ch ) , 111.5 ( 5.2 chaaaa ) , 111.4 ( 8.2 chaaaa ) , 61.7 ( 14 ch2 ) , 56.1 ( 14 ch3 ) , 53.3 ( 14 ch ) , 37.2 ( 14 ch2 ) , 14.2 ( 14 ch3 ) ppm . tg = 134 c ; tp = 350 c . to a solution of 11 ( 532.5 
 mg , 1.07 mmol ) in ch2cl2 ( 12 ml ) were added 
 diphosgene ( 79 l , 0.66 mmol ) and a catalytic amount of activated 
 charcoal .
the solution was cooled to 45 c , and n , n - dimethylaniline ( 0.24 
 ml , 1.92 mmol ) was added dropwise .
the reaction was allowed to stir 
 at 45 c and then warmed slowly to room temperature and 
 reacted overnight .
the salts and activated charcoal were removed by 
 filtration , and the solvent was removed under vacuum .
the product 
 was purified by flash chromatography ( 24 g , 0% to 50% of acoet in 
 hexane over 20 min ) to lead to a white foam ( 492.8 mg , 0.88 mmol , 
 82% ) .
ftir ( atr ) max ( cm ) : 1790 , 
 1738 , 1659 , 1632 , 1510 .
h nmr spectrum ( 500 mhz , cdcl3 )  : 7.57 ( d , j = 15.6 hz , 1 h ) , 7.15 
 ( d , j = 8.7 hz , 1 h ) , 7.137.06 ( m , 2 h ) , 
 6.97 ( d , j = 8.4 hz , 2 h ) , 6.75 ( d , j = 8.4 hz , 2 h ) , 6.36 ( d , j = 15.6 hz , 1 h ) , 6.12 
 ( d , j = 7.7 hz , 1 h ) , 4.96 ( dt , j = 7.7 , 5.6 hz , 1 h ) , 4.20 ( q , j = 7.2 hz , 2 h ) , 
 3.91 ( s , 3 h ) , 3.14 ( dd , j = 5.6 , 2.6 hz , 2 h ) , 1.28 
 ( t , j = 7.1 hz , 3 h ) , 0.97 ( s , 9 h ) , 0.17 ( s , 6 h ) 
 ppm .
c nmr spectrum ( 125 mhz , cdcl3 )  : 
 171.6 ( c ) , 164.7 ( c ) , 154.8 ( c ) , 150.7 ( c ) , 148.9 ( c ) , 141.5 ( c ) , 
 140.4 ( c ) , 135.0 ( ch ) , 130.4 ( 2 ch ) , 128.3 ( c ) , 122.1 ( ch ) , 121.3 
 ( ch ) , 120.7 ( ch ) , 120.1 ( 2 ch ) , 111.5 ( ch ) , 61.6 ( ch2 ) , 
 56.1 ( ch3 ) , 53.4 ( ch ) , 37.1 ( ch2 ) , 25.6 ( 3 ch3 ) , 18.2 ( c ) , 14.2 ( ch3 ) , 4.4 ( 2 ch3 ) ppm . in the glovebox , a mixture of 14 ( 198 mg , 
 0.35 mmol ) and agf ( 89.4 mg , 0.70 mmol ) was prepared . then outside 
 of the glovebox , acetonitrile ( 0.14 ml ) and pyridine ( 0.56 ml ) were 
 added .
the mixture was ventilated with a cartridge containing naoh 
 to quench fumes of phosgene .
the reaction mixture was stirred at room 
 temperature for 15 min and was quenched with a saturated solution 
 of nahco3 .
the mixture was solubilized in dmf , filtered 
 through a pad of celite , then precipitated out into meoh three times , 
 and dried under vacuum to give the desired product as a white solid 
 which follows aaaa , aaaa , aaaa 
 patterns in 5/5/90 proportions ( 80.9 mg , 0.20 mmol , 57% ) .
ftir ( atr ) 
 max ( cm ) : 33003200 , 
 1789 , 1737 , 1659 , 1622 , 1510 .
h nmr spectrum ( 500 mhz , d6-dmso )  : 8.678.47 ( m , 20 h ) , 
 7.577.12 ( m , 160 h ) , 6.72 ( d , j = 15.9 hz , 
 20 h ) , 4.684.54 ( m , 20 h ) ,
4.183.98 ( m , 40 h ) , 3.89 
 ( br s , 60 h ) , 3.202.86 ( m , 40 h ) , 1.350.94 ( m , 60 
 h ) ppm .
c nmr spectrum ( 125 mhz , d6-dmso )  : 171.5 ( 20 c ) , 164.9 ( 20 c ) , 151.7 ( 2 c(o)aaaa ) , 150.94 ( 16 caaaa ) , 150.88 ( 4 caaaa ) , 150.8 ( 16 c(o)aaaa ) , 150.4 ( 2 caaaa ) , 149.4 ( 20 c ) , 140.1 ( 20 c ) , 138.8 ( 20 ch ) , 135.5 ( 16 caaaa ) , 135.4 ( 4 caaaa ) , 134.5 ( 16 caaaa ) , 134.4 ( 4 caaaa ) , 130.4 ( 32 chaaaa ) , 130.3 ( 8 chaaaa ) , 122.7 ( 20 ch ) , 122.1 
 ( 20 ch ) , 121.0 ( 8 chaaaa ) , 120.8 ( 32 chaaaa ) , 120.3 ( 20 ch ) , 111.8 ( 20 ch ) , 60.6 ( 20 
 ch2 ) , 56.05 ( 20 ch3 ) , 53.8 ( 20 ch ) , 36.1 ( 20 
 ch2 ) , 14.0 ( 20 ch3 ) ppm .
tg = 129 c , tp = 337 c . to a solution of 11 ( 1.1 g , 2.2 mmol ) and 
 4-nitrophenyl chloroformate ( 225.2 mg , 1.1 mmol ) in ch2cl2 ( 2.2 ml ) , at room temperature was added et3n ( 0.46 ml , 3.3 mmol ) .
the residue was purified 
 by flash chromatography on a silica cartridge ( 40 g , hexane / acoet 
 0 to 60% over 30 min ) .
the desired product was obtained as a white 
 foam ( 657.8 mg , 0.64 mmol , 58% , brm : 84% ) .
ftir ( atr ) max ( cm ) : 1782 , 1732 , 1667 , 1508 .
h nmr spectrum ( 500 mhz , cdcl3 )  : 7.54 ( d , j = 15.6 hz , 2 h ) , 7.20 ( d , j = 8.7 hz , 
 2 h ) , 7.087.05 ( m , 4 h ) , 6.99 ( d , j = 8.4 
 hz , 4 h ) , 6.75 ( d , j = 8.4 hz , 4 h ) , 6.37 ( d , j = 7.1 hz , 2 h ) , 6.36 ( d , j = 15.6 hz , 
 2 h ) , 4.95 ( dt , j = 7.9 , 5.8 hz , 2 h ) , 4.18 ( qd , j = 7.1 , 2.3 hz , 4 h ) , 3.90 ( s , 6 h ) , 3.183.01 ( m , 
 4 h ) , 1.26 ( t , j = 7.1 hz , 6 h ) , 0.96 ( s , 18 h ) , 
 0.16 ( s , 12 h ) ppm . c nmr spectrum ( 125 mhz , cdcl3 )  : 171.4 ( 2 c ) , 154.7 ( 2 c ) , 151.2 ( 2 c ) , 150.7 ( c ) , 
 141.0 ( 2 c ) , 140.7 ( 2 ch ) , 134.1 ( 2 c ) , 130.3 ( 4 ch ) , 128.4 ( 2 c ) , 
 122.5 ( 2 ch ) , 120.7 ( 2 ch ) , 120.6 ( 2 ch ) , 120.0 ( 4 ch ) , 111.5 ( 2 ch ) , 
 61.5 ( 2 ch2 ) , 56.0 ( 2 ch3 ) , 53.5 ( 2 ch ) , 37.0 
 ( 2 ch2 ) , 25.6 ( 6 ch3 ) , 18.1 ( 2 c ) , 14.1 ( 2 ch3 ) , 4.5 ( 6 ch3 ) ppm . ms ( esi / maldi ) m / z ( % ) not detected . to a solution of 15 ( 4.76 
 g , 4.93 mmol ) in ch2cl2 ( 25 ml ) was added dropwise 
 bf3oet2 ( 2.5 ml , 19.7 mmol ) .
the reaction 
 was stirred at room temperature for 23 h. a saturated solution of 
 nahco3 was added , and the crude was extracted with ch2cl2 , dried over na2so4 , and 
 filtered .
the residue was purified 
 by flash chromatography on a silica cartridge ( 4 g , hexane / acoet 0 
 to 100% over 15 min ) .
the desired product was obtained as a white 
 foam ( 2.55 g , 3.2 mmol , 65% ) .
ftir ( atr ) max ( cm ) : 36003100 , 1784 , 1738 , 1661 , 1614 , 1512 .
h nmr spectrum ( 500 mhz , d8-thf ) 
  : 8.18 ( s , 2 h ) , 7.53 ( d , j = 15.6 hz , 2 h ) , 
 7.46 ( d , j = 8.0 hz , 2 h ) , 7.26 ( d , j = 1.8 hz , 2 h ) , 7.17 ( d , j = 8.2 hz , 2 h ) , 7.12 
 ( dd , j = 8.2 , 1.8 hz , 2 h ) , 6.97 ( d , j = 8.4 hz , 4 h ) , 6.666.59 ( m , 6 h ) , 4.83 ( dt , j = 8.0 , 6.3 hz , 2 h ) , 4.11 ( q , j = 7.1 hz , 4 h ) , 
 3.88 ( s , 6 h ) , 3.05 ( dd , j = 13.9 , 6.3 hz , 2 h ) , 
 2.96 ( dd , j = 13.9 , 6.7 hz , 2 h ) , 1.20 ( t , j = 7.1 hz , 6 h ) ppm .
c nmr spectrum ( 125 mhz , d8-thf )  : 172.2 ( 2 c ) , 165.3 ( 2 c ) , 157.3 
 ( 2 c ) , 152.3 ( 2 c ) , 151.1 ( c),141.8 ( 2 c ) , 140.0 ( 2 ch ) , 135.6 ( 2 
 c ) , 130.8 ( 4 ch ) , 127.9 ( 2 c ) , 123.0 ( 2 ch ) , 122.4 ( 2 ch ) , 120.7 ( 2 
 ch ) , 115.7 ( 4 ch ) , 112.4 ( 2 ch ) , 61.3 ( 2 ch2 ) , 56.01 ( 2 
 ch3 ) , 54.5 ( 2 ch ) , 37.7 ( 2 ch2 ) , 14.3 ( 2 ch3 ) ppm .
h nmr spectrum ( 500 mhz , d6-dmso )  : 9.24 ( s , 2 h ) , 8.48 ( d , j = 7.7 hz , 2 h ) , 7.447.37 ( m , 4 h ) , 7.34 ( d , j = 8.2 hz , 2 h ) , 7.21 ( dd , j = 8.4 , 1.8 hz , 2 h ) , 
 7.02 ( d , j = 8.5 hz , 4 h ) , 6.74 ( d , j = 15.8 hz , 2 h ) , 6.66 ( d , j = 8.5 hz , 4 h ) , 4.52 
 ( ddd , j = 8.8 , 7.7 , 5.8 hz , 2 h ) , 4.06 ( q , j = 7.1 hz , 4 h ) , 3.91 ( s , 6 h ) , 2.95 ( dd , j = 13.9 , 5.8 hz , 2 h ) , 2.86 ( dd , j = 13.9 , 8.8 hz , 
 2 h ) , 1.13 ( t , j = 7.1 hz , 6 h ) ppm . c nmr spectrum ( 125 mhz , d6-dmso )  : 
 171.7 ( 2 c ) , 164.8 ( 2 c ) , 156.0 ( 2 c ) , 150.9 ( 2 c ) , 150.4 ( c(o)aaaa),140.1 ( 2 c ) , 138.6 ( 2 ch ) , 134.5 ( 2 c ) , 
 130.0 ( 4 ch ) , 127.0 ( 2 c ) , 122.7 ( 2 ch ) , 122.3 ( 2 ch ) , 120.3 ( 2 ch ) , 
 115.1 ( 4 ch ) , 111.9 ( 2 ch ) , 60.5 ( 2 ch2 ) , 56.1 ( 2 ch3 ) , 54.2 ( 2 ch ) , 36.2 ( 2 ch2 ) , 14.0 ( 2 ch3 ) ppm . ms ( esi / apci / maldi ) m / z not detected . to a solution of 16
( 122.1 
 mg , 0.15 mmol ) in pyridine ( 0.60 ml ) at 0 c was added dropwise 
 diphosgene ( 21 l , 0.17 mmol ) .
the mixture was ventilated with 
 a cartridge containing naoh to quench fumes of phosgene .
the reaction 
 mixture was stirred at room temperature for 2 h and was quenched with 
 a saturated solution of nahco3 .
the product was an orange 
 gel which was solubilized in warm dmf / dmso mixture and precipitated 
 out into meoh three times and dried under vacuum to give the desired 
 product as a white / yellowish solid which follows an aaaa 
 pattern ( 91.3 mg , 0.11 mmol , 73% ) .
ftir ( atr ) max ( cm ) : 34003200 , 1776 , 1736 , 
 1667 , 1625 , 1601 , 1504 .
h nmr spectrum ( 500 mhz , d6-dmso )  : 8.60 ( d , j = 7.6 hz , 45 h ) , 7.42 ( d , j = 15.6 hz , 45 h ) , 7.417.24 
 ( m , 315 h ) , 7.247.17 ( m , 45 h ) , 6.72 ( d , j = 15.8 hz , 45 h ) , 4.61 ( q , j = 7.8 hz , 45 h ) , 4.06 
 ( q , j = 6.8 hz , 90 h ) , 3.90 ( s , 135 h ) , 3.142.95 
 ( m , 90 h ) , 1.11 ( t , j = 7.1 hz , 135 h ) ppm .
c nmr spectrum ( 125 mhz , d6-dmso ) 
  : 171.5 ( 45 c ) , 164.9 ( 45 c ) , 151.7 ( 23 c(o)aaaa ) , 150.9 ( 45 c ) , 150.4 ( 22 c(o)aaaa ) , 
 149.4 ( 45 c ) , 140.1 ( 45 c ) , 138.8 ( 45 ch ) , 135.4 ( 45 c ) , 134.5 ( 45 
 c ) , 130.3 ( 90 ch ) , 122.7 ( 45 ch ) , 122.1 ( 45 ch ) , 121.0 ( 90 ch ) , 120.3 
 ( 45 ch ) , 112.0 ( 45 ch ) , 60.6 ( 45 ch2 ) , 56.08 , 56.06 ( 45 
 ch3 ) , 53.8 ( 45 ch ) , 36.1 ( 45 ch2 ) , 14.0 ( 45 
 ch3 ) ppm . tg = 130 c , tp = 343 c . to a solution of 8 ( 70.3 mg , 0.18 mmol ) in pyridine 
 ( 0.34 ml ) at 0 c was added dropwise diphosgene ( 12 l , 
 0.10 mmol ) .
the mixture was ventilated with a cartridge containing 
 naoh to quench fumes of phosgene .
the reaction mixture was stirred 
 at room temperature for 15 h and was quenched with a saturated solution 
 of nahco3 .
the product was extracted with ch2cl2 and dried over na2so4 , and the 
 solvent was removed under vacuum .
the brown film formed was solubilized 
 in ch2cl2 , precipitated into meoh three times , 
 and dried under vacuum to give the desired product as a brownish solid 
 which follows aaaa , aaaa , aaaa 
 patterns in 37/23/40 proportions ( 35.4 mg , 0.086 mmol , 48% ) . during 
 the reaction ,
a yellow solid part was formed , insoluble in ch2cl2 , chcl3 , pyridine , dmf , dmso , acetone , 
 and h2o even after sonication and heating .
this insoluble 
 fraction could not be analyzed and consequently may explain the lower 
 yield observed .
ftir ( atr ) 
 max ( cm ) : 34003200 , 
 1778 , 1732 , 1666 , 1628 , 1504 .
h nmr spectrum ( 500 mhz , 
 cdcl3 )  : 7.53 ( br d , j = 15.0 hz , 
 36 h ) , 7.226.93 ( m , 238 h ) , 6.476.22 ( m , 72 h ) , 5.044.93 
 ( m , 36 h ) , 4.18 ( br q , j = 7.2 , 6.5 hz , 72 h ) , 3.86 
 ( br s , 108 h ) , 3.283.11 ( m , 72 h ) , 1.42- 1.02 ( m , 108 h ) ppm .
h nmr spectrum ( 500 mhz , d6-dmso ) 
  : 8.60 ( br d , j = 7.7 hz , 36 h ) , 7.477.15 
 ( m , 252 h ) , 6.766.65 ( m , 72 h ) , 4.644.57 ( m , 36 h ) , 
 4.104.01 ( m,72 h ) , 3.89 ( br s , 108 h ) , 3.172.93 ( m , 
 72 h ) , 1.11 ( br t , j = 7.1 hz , 108 h ) ppm .
c nmr spectrum ( 125 mhz , cdcl3 )  : 171.5 ( 36 c ) , 
 165.1 ( 36 c ) , 152.0 ( 8.3 c(o)aaaa ) , 151.3 
 ( 14.4 caaaa ) , 151.1 ( 21.6 caaaa ) , 150.7 ( 14.4 c(o)aaaa ) , 150.2 ( 13.3 
 c(o)aaaa ) , 150.0 ( 36 c ) , 141.1 , 141.0 , 
 140.9 ( 36 ch + 36 c ) , 134.1 , 134.0 ( 72 c ) , 130.52 , 130.49 ( 72 ch ) , 
 122.6 ( 14.4 chaaaa ) , 122.5 ( 21.6 chaaaa ) , 120.94 , 120.89 , 120.8 ( 72 ch ) , 120.6 
 ( 36 ch ) , 111.4 ( 21.6 chaaaa ) , 61.8 ( 36 
 ch2 ) , 56.1 ( 21.6 ch3aaaa ) , 56.0 
 ( 14.4 ch3aaaa ) , 53.3 ( 36 ch ) , 37.2 ( 36 
 ch2 ) , 14.2 ( 36 ch3 ) ppm . c nmr 
 spectrum ( 125 mhz , d6-dmso )  : 171.4 
 ( 34 c ) , 165.9 ( 34 c ) , 151.6 ( 8.3 c(o)aaaa ) , 150.93 ( 14.4 caaaa ) , 150.87 ( 21.6 caaaa ) , 150.8 ( 14.4 c(o)aaaa ) , 150.3 ( 13.3 c(o)aaaa ) , 149.4 ( 36 c ) , 
 140.1 ( 36 c ) , 138.7 ( 36 c ) , 135.5 ( 14.4 caaaa ) , 135.4 ( 21.6 caaaa ) , 134.44 ( 14.4 caaaa ) , 134.38 ( 21.6 caaaa ) , 130.4 ( 28.8 chaaaa ) , 130.3 ( 43.2 chaaaa ) , 122.6 ( 36 ch ) , 122.1 ( 36 ch ) , 121.0 
 ( 43.2 chaaaa ) , 120.8 ( 28.8 chaaaa ) , 120.3 ( 36 ch ) , 111.9 ( 21.6 chaaaa ) , 
 111.8 ( 14.4 chaaaa ) , 60.6 ( 36 ch2 ) , 56.1 ( 36 ch3 ) , 53.8 ( 36 ch ) , 36.1 ( 36 ch2 ) , 14.0 ( 36 ch3 ) ppm .
we envisioned that the poly(carbonate  amide)s 
 could be synthesized 
 readily either by copolycondensation of a diol with a phosgene derivative 
 or by homopolycondensation of an ab monomer obtained by prior conversion 
 of one of the alcohol groups to an activated carbonate or chloroformate . 

the required diol monomer would first be obtained by coupling fa to 
 a hydroxyl - containing amino acid by means of a peptidic bond ( scheme 1 ) .
this approach would enable degradation to occur 
 via two distinct pathways : aqueous hydrolysis of the carbonate bond 
 and enzymatic cleavage of the amide bond . among the naturally occurring amino acids , serine , with its more 
 reactive primary alcohol ,
was expected to be the most attractive coupling 
 partner , followed by threonine , which contains a less reactive secondary 
 alcohol , and finally tyrosine , which features a phenolic functionality 
 that could lead to solubility issues for high molecular weight polymers .
an ab monomer activated as a p - nitrophenyl carbonate 4 was initially designed , as 
 the polymerization of similar species has been reported in the literature .
this monomer was preferred to its more reactive 
 chloroformate analogue because the synthesis of the latter requires 
 the manipulation of phosgene derivatives .
the monomer synthesis 
 began from the commercially available l - serine , which was 
 protected as its ethyl ester .
this protection step 
 was necessary to selectively convert the hydroxyl group to a silyl 
 ether derivative and also for the later selective amidation with ferulic 
 acid ( scheme 2 ) .
the tbdms protecting group 
 is cleavable under mild acidic conditions and was chosen for its stability 
 under basic conditions used in the following steps .
a peptidic coupling 
 of this intermediate with ferulic acid generated 2 in 
 two steps ( 51% ) .
the structure was confirmed by the presence of a 
 signal attributed to the quaternary carbon peak of the amide by c nmr ( 165.8 ppm ) and by ftir ( 1658 cm ) spectroscopies .
the p - nitrophenyl carbonate 3 was synthesized in 84% yield by reaction of the phenol with p - nitrophenyl chloroformate in the presence of pyridine . 

subsequent deprotection by boron trifluoride provided the activated 
 ab monomer 4 ( 88% ) .
formation of the carbonate link in 3 and 4 was confirmed by both c 
 nmr ( 150.3 ppm ) and ftir ( 1778 , 1784 cm ) spectroscopies . 

a doublet of triplets at 2.49 ppm by h nmr spectroscopy , 
 as well as a broad band around 32003400 cm by ftir spectroscopy , confirmed the presence of a free alcohol in 4 .
unfortunately , rather than 
 undergoing polymerization , 4 led to an elimination product 5 upon treatment with 
 base .
no reaction occurred during our first attempt at polymerizing 
 monomer 4 in the presence of pyridine , and the starting 
 material was recovered unchanged .
the use of a stronger base , triethylamine , 
 did not lead to a polymer either .
further details confirming the structure of 
 the former compound are presented in the supporting 
 information .
alternatively , the introduction of the activated p - nitrophenyl carbonate on the primary alcohol of the serine 
 residue 
 was not attempted .
we reasoned that the presence of such an electron - withdrawing 
 group would most likely enhance the acidity of the proton on the -carbon 
 of the amino acid residue , favoring the elimination pathway .
tyrosine was selected over threonine in order 
 to avoid any possible side reaction on the -carbon of the amino 
 acid residue in the activated monomer . in an attempt to minimize the 
 toxicity of the products potentially released during degradation of 
 the polymers , the commercially available l - tyrosine ethyl 
 ester , which would generate ethanol upon hydrolysis , was used as a 
 starting building block ( rather than use of a methyl ester that would 
 generate methanol ) .
interestingly , the natural amides ( e)-n-(feruloyl)-l - tyrosine methyl ester 6 and tert - butyl ester 7 have 
 already been synthesized and tested biologically ( figure 1 ) .
a stronger antioxidant 
 effect was revealed for the more sterically hindered tert - butyl ester when compared with the methyl ester , and both surpassed 
 ferulic acid in lipid peroxidation assays .
the anticipated hydrolytic degradation product of a fa  tyrosine - based 
 poly(carbonate  amide ) system , ( e)-n-(feruloyl)-l - tyrosine ethyl ester 8 ( figure 1 ) , may , therefore , present a bioactivity 
 similar to its methyl and tert - butyl counterparts . 
 based upon this strategy ,
a series of four monomers were synthesized , 
 having functionalities installed that would allow for condensation 
 polymerization via carbonate formation and including regiochemistries 
 that would produce either head - to - tail , tail - to - head - to - head - to - tail , 
 or random sequences in the resulting poly(carbonate  amide)s .
a monoactivated ba monomer 
 was initially designed in order to synthesize a regioregular aaaa 
 ( head - to - tail ) polymer , where a is the phenol of fa , a is 
 the phenol of tyrosine , and b is an activated carbonate or chloroformate 
 derivative of the fa phenol .
the p - nitrophenyl carbonate 
 ba monomer 13 was targeted first using the same 
 synthetic pathway as described above for 4 .
the phenol 
 group of the tyrosine ethyl ester hydrochloride 9 was 
 protected with tbdmscl , resulting in 10 ( 81% ) .
the free alcohol of 11 was activated to a p - nitrophenyl carbonate 12 in the presence of pyridine ( 71% ) . finally , the deprotection 
 of 12 under mild conditions afforded the activated ba 
 monomer 13 in high yield ( 85% ) .
c nmr and 
 ftir spectroscopies confirmed both the formation of the carbonate 
 and the deprotection of the phenol group ( scheme 3 ) .
polymerizations were conducted in the presence of a base 
 to generate 
 the nucleophilic phenoxide group .
optimization of the experimental 
 conditions was performed through variation of the solvents ( ch2cl2 and pyridine ) , the initial monomer concentration 
 ( 1 m , 3 m ) , the base ( et3n , pyridine , dipea , dmap or a 
 mixture ) , the reaction times ( 5 to 72 h ) , and temperatures ( rt , 50 
 c , 95 c ) .
the outcomes of the reactions were evaluated 
 in terms of the final degree of polymerization ( dpn ) , as 
 determined by sec .
the reliability of the number - average molecular 
 weights ( mn ) determined against peo calibration 
 was confirmed by comparison with the mn obtained from a relative calibration performed from the oligomeric 
 fraction contained in the crude polymerization mixture ( table s1 , 
 see details in supporting information ) . 
 also , chain - end functionalization of the polymers with reactive capping 
 agents ( allylchloroformate and furfuryl isocyanate ) and their subsequent 
 analysis by h nmr spectroscopy gave further support to 
 the dpn values that are reported and also revealed that 
 the primary component of the system is an acyclic polymer ( see details 
 in supporting information ) . despite parametrization
, 
 all the reactions resulted in polymers with dpn values 
 limited to a range of 1520 , according to sec and h nmr spectroscopic measurements .
one of the samples was further 
 characterized by c nmr spectroscopy to obtain insight 
 into the regioselectivity of the polymerizations .
surprisingly , the 
 analysis of the spectrum showed evidence of the formation of all three 
 possible regioisomers ( head - to - tail , head - to - head , tail - to - tail ) in 
 the isolated polymer ( vide infra ) , instead of the 
 expected aaaa ( head - to - tail ) regiospecificity as implied 
 by monomer design .
the poor regioselectivity and the limited dpn achieved can plausibly be explained by the release of a p - nitrophenolate , which may act as an additional nucleophile 
 able to attack the polymeric carbonyl - based backbone and promote exchange 
 reactions or by the insufficient difference in the leaving group ability 
 of p - nitrophenol and the fa phenol .
determined 
 by sec ( dmf , 0.05 m libr ) 
 using oligomer calibration . determined by c nmr 
 spectroscopy . in an attempt 
 to minimize regiorandomness and achieve higher dpn , the 
 alcohol 11 was converted to the more reactive 
 chloroformate 14 by reaction with either diphosgene , which gave the best yield ( 82% ) , or triphosgene ( 70% ) ( scheme 3 ) . despite 
 the lower yield , triphosgene was preferred because of its ease of 
 use .
the presence of a chloroformate functionality in 14 was confirmed by c nmr ( 148.9 ppm ) and ftir ( 1790 cm ) spectroscopies .
interestingly , this new ba 
 monomer , designed to generate a polymer with higher regioregularity 
 and molecular weight , was obtained in only three synthetic steps . 

the polymerization was then triggered by the deprotection of the phenol 
 silyl ether , which generated the propagating nucleophile in a single 
 sequence .
several sources of fluoride such as tetrabutylammonium 
 fluoride , 
 potassium fluoride , cesium fluoride , and silver fluoride were evaluated 
 for the deprotection of the silyl ether to the phenolate . among them , 
 silver fluoride , which drove the reaction by precipitation of silver 
 chloride , was the most promising and afforded oligomers .
the screening 
 of solvents ( pyridine , pyridine / ch3cn , thf / ch3cn , or ch3cn ) revealed the necessity of both ch3cn ( agf solubility ) and pyridine ( polymer solubility ) to achieve 
 polymerization .
the use of 2 equiv of agf proved necessary to obtain 
 high dpn values , whereas higher loadings complicated the 
 purification process .
although no effect of the reaction temperature 
 ( rt vs 60 c ) was observed , a marked effect of the initial monomer 
 concentration was noticed . in dilute media ( 0.1 m )
only small oligomers 
 were formed ( supporting information , table 
 s3 , entry 1 ) while some precipitate was noticeable at 0.5 m ( entry 
 3 ) , and the reaction mixture almost instantaneously crashed out of 
 solution at even higher concentration ( 0.75 m , entry 4 ) .
a kinetic 
 study was performed at an intermediate concentration of 0.5 m ( entries 
 58 ) .
after 1.5 h , a polymer of mn = 11.1 kg mol (  = 1.92 ) was extracted with a low yield ( 14% ) from 
 the heterogeneous reaction mixture .
reduction of the reaction time 
 down to 15 min facilitated the work - up and led to a polymer of mn = 8.3 kg mol (  = 2.08 , dpn = 20 ) with a decent yield ( 56% ) .
the corresponding polymers 
 exhibited a high degree of aaaa ( head - to - tail ) regioselectivity 
 as inferred from c nmr spectroscopic measurements . with the aaaa 
 polymer in our hands
, we then sought to synthesize the aaaa 
 polymer with a high regioselectivity by polycondensation of the dimeric 
 monomer 16 .
the aaaa monomer 16 was obtained from 11 by dimerization , using p - nitrophenyl chloroformate as an activating reagent , followed 
 by deprotection of the phenol groups under mild conditions ( scheme 4 ) .
the initial formation of the carbonate bond between 
 the two fa subunits in 16 was performed because of the 
 potentially lower reactivity of the corresponding phenols during the 
 polymerization process ( steric hindrance of the o - methoxy group ) . also , this strategy allowed for ready attribution 
 of the peak at 150.4 ppm to the carbonate in an aaaa 
 sequence in the c nmr spectrum , which is necessary to 
 quantify the relative ratio of regioisomers in the polymers .
the desired aaaa 
 polymer was obtained by polycondensation 
 of the diphenol 16 with a phosgene derivative .
a first 
 set of experiments performed in pyridine , which acted as a base and 
 solvent , revealed that neat diphosgene was more effective at promoting 
 polycondensation than was triphosgene .
optimization of the reaction 
 conditions , such as the initial monomer concentration , the diphosgene 
 feed ratio , and the reaction time , led to the isolation of a high 
 molecular weight aaaa polymer of mn = 18.0 kg mol (  = 2.06 , dpn = 44 ) in 
 2 h with 74% yield ( supporting information , table s4 ) .
detailed c nmr spectroscopic analyses revealed 
 the presence of only two signals attributed to carbonate groups ( 150.4 
 and 151.7 ppm for the fa  fa carbonate of the monomer aaaa 
 and the newly established tyrosine 
tyrosine carbonate aaaa 
 sequences , respectively ) which confirmed the high regioselectivity 
 of the aaaa polymer ( figure 2 ) .
c nmr attribution of carbonyl carbons corresponding 
 to the carbonate functionalities of the fa 
fa coupling aaaa 
 in monomer 16 ( black ) , the newly established tyrosine 
tyrosine 
 couplings aaaa of the resulting polymer ( blue ) , the 
 predominance of fa 
tyrosine couplings aaaa 
 from the polymerization of 14 and all three types of 
 carbonate carbonyls from the random couplings of fa and tyrosine groups 
 during the polymerization of 8 . in order to fully realize a fa - co - tyrosine strategy for the generation of bio - derived poly(carbonate 
the so - called 
 aa monomer 8 was obtained in only one step ( 67% ) 
 by peptidic coupling of commercially available fa and l - tyrosine 
 ethyl ester hydrochloride ( scheme 5 ) .
the formation 
 of the amide linkage in 8 was confirmed by spectroscopic 
 characterization .
polymerization conditions were 
 based on those employed during the 
 polymerization of monomer 16 ; modifying the diphosgene 
 equivalency , the global concentration and the reaction time , a polymer 
 of mn
= 14 kg mol (  : 2.57 , dpn = 34 ) was obtained ( 47% ) ( supporting 
 information , table s5 ) .
the relative ratio of the three types 
 of carbonates , having tyrosine  tyrosine , fa  fa , and 
 tyrosine 
fa couplings , aaaa , aaaa , 
 and aaaa sequences , respectively , present in the polymer 
 was found to be 37:23:40 , as determined by the integration of the c nmr signals of the carbonate carbonyl carbon ( figure 2 ) .
it is clear that the aaaa and 
 aaaa sequences are more prevalent than the aaaa 
 sequence in the regiorandom polymer sample .
this lack of true regiorandomness 
 could be rationalized by a lower reactivity of the phenolic group 
 from the fa subunit vs the one from the tyrosine 
 residue during polycondensation because of a higher steric hindrance . 

a summary of the properties of this regiorandom polymer is provided 
 table 1 , entry 4 .
the thermal stability of all four 
 polymers has been assessed by thermogravimetric analysis ( tga ) and 
 differential scanning calorimetry ( dsc ) ( table 1 ) .
tg < 135 c ) 
 and the first derivative tga peak ( 337 c < tp < 351 c ) for each of the polymers under investigation 
 reveals that the thermal properties were not influenced by the regiochemistry . 

the thermal stability of a representative polymer sample ( aaaa 
 polymer from 13 ) was compared to the monomer ( 8)/multimer ( 16 ) and the starting materials ( figure 3 ) . as expected ,
the aa and aaaa 
 monomers ( 8 and 16 , respectively ) were less 
 thermally stable than the polymer ( 318 and 328 c , respectively ) 
 and more stable than the l - tyrosine ethyl ester ( 224 , 276 , 
 and 375 c ) and fa ( 243 c ) .
high residual masses were observed 
 at 500 c for all polymers as well as for monomer 8 and multimer 16 . this stability may plausibly be explained 
 by the formation of highly conjugated structures .
thermogravimetric analysis 
 of aaaa polymer from 13 , aa monomer 8 , aaaa 
 monomer 16 , fa , and tyrosine .
fluorescent properties of fa 
 and tyrosine have been investigated in the past , and these compounds 
 have been used as probes for assessing intermolecular interactions as well as fa proportion and disposition in food . a recent study of tyrosine s three - dimensional emission 
 spectra provided a way to distinguish tyrosine from tryptophan , which 
 can find applications in the analysis of deep sea chemistries . because of these fluorescent properties in the 
 starting materials ( supporting information , figures s4 and s5 ) , a comparison of absorbance , excitation , and 
 emission spectra of the aa monomer 8 and the 
 random polymer was obtained , revealing a shift in the maximum wavelength 
 in the emission spectra from 394 nm ( 8) to 427 nm ( random 
 polymer from 8) ( figure 4 ) .
these 
 initial results displayed a variation in the fluorescence properties 
 of the monomer and the polymer .
this red - shift to a material that 
 is suited to 350 nm excitation and 430 nm emission regimes makes the 
 emissivity of the random polymers viable for their immediate use as 
 imaging agents , employing one of the most common imaging modalities 
 in microscopy ( dapi filter set ) .
absorbance , 
 excitation , and emission spectra for ( a ) monomer 8 and 
 ( b ) the corresponding regiorandom polymer .
the design and synthesis of a poly(carbonate  amide ) 
 based 
 on fa , a renewable and biocompatible resource present in fruits and 
 vegetables , has been reported . in order to generate a poly(carbonate 
amide ) 
 by polycondensation , fa was coupled to a hydroxyl - amino acid via an 
 amide link .
l - serine couple was synthesized but failed to polymerize . moving to 
 an l - tyrosine partner led to the generation of an array of 
 new fa 
a good overall control 
 of the regioselectivity of the resulting polymers was achieved by 
 careful design of the monomers and led to the synthesis of poly(carbonate 
amide)s 
 possessing head - to - head , tail - to - tail , and head - to - tail sequences 
 in a nearly regiospecific fashion .
although the glass transition and thermal degradation properties 
 of the fa  tyrosine - based poly(carbonate - amide)s ( tg and tp ) were not significantly 
 influenced by the regioselectivity or the chain length , preliminary 
 results on the fluorescent properties showed a shift in the maximum 
 of the excitation and emission spectra between the aa monomer 8 and the corresponding random polymer .
further fluorescence 
 studies are underway to probe the imaging promise of this new class 
 of bio - derived poly(carbonate  amide)s .
amide)s derived from fa and a hydroxyl - containing 
 amino acid could potentially undergo hydrolytic breakdown and lead 
 to biologically beneficial byproducts and carbon dioxide .
moreover , 
 the rigidity of both fa and tyrosine subunits as well as the polar , 
 hydrogen - bonding amide groups may lead to materials with enhanced 
 mechanical properties .
specifically , applications would include 
 engineering plastics , biomedical components , and other applications 
 where mechanical strength and degradation are both desired .
 ferulic acid ( fa ) , a bio - based resource 
 found in fruits and vegetables , 
 was coupled with a hydroxyl - amino acid to generate a new class of 
 monomers to afford poly(carbonate  
 amide)s with potential to 
 degrade into natural products . 
 l - serine was first selected 
 as the hydroxyl - amino partner for fa , from which the activated p - nitrophenyl carbonate monomer was synthesized . 
 unfortunately , 
 polymerizations were unsuccessful , and the elimination product was 
 systematically obtained . to avoid elimination , we revised our strategy 
 and used l - tyrosine ethyl ester , which lacks an acidic proton 
 on the  position of the ethyl ester . 
 four new monomers were 
 synthesized and converted into the corresponding poly(carbonate  
 amide)s 
 with specific regioselectivities . 
 the polymers were fully characterized 
 through thermal and spectroscopic analyses . 
 preliminary fluorescent 
 studies revealed interesting photophysical properties for the monomers 
 and their corresponding poly(carbonate  amide)s , beyond the 
 fluorescence characteristics of l - tyrosine and fa , making 
 these materials potentially viable for sensing and/or imaging applications , 
 in addition to their attractiveness as engineering materials derived 
 from renewable resources . 
Introduction
Experimental Section
Results
and Discussion
Conclusions