This work demonstrates for the first-time biobased, temperature-responsive
diblock copolymer nanoparticles synthesized by reversible addition–fragmentation
chain-transfer (RAFT) aqueous emulsion polymerization-induced self-assembly
(PISA). Here, monomers derived from green solvents of the lactic acid
portfolio,N,N-dimethyl lactamide acrylate (DMLA)
and ethyl lactate acrylate (ELA), were used. First, DMLA was polymerized
by RAFT aqueous solution polymerization to produce a hydrophilic PDMLA
macromolecular chain transfer agent (macro-CTA), which was chain extended
with ELA in water to form amphiphilic PDMLA-b-PELA
diblock copolymer nanoparticles by RAFT aqueous emulsion polymerization.
PDMLAxhomopolymers were synthesized targeting
degrees of polymerization, DPxfrom 25
to 400, with relatively narrow molecular weight dispersities (Đ< 1.30). The PDMLA64-b-PELAydiblock copolymers (DPy= 10–400) achieved dispersities,Đ, between 1.18 and 1.54 with two distinct glass transition
temperatures (Tg) identified by differential
scanning calorimetry (DSC).Tg(1)(7.4
to 15.7 °C) representative of PELA andTg(2)(69.1 to 79.7 °C) of PDMLA. Dynamic light scattering
(DLS) studies gave particle z-average diameters between 11 and 74
nm (PDI = 0.04 to 0.20). Atomic force microscopy (AFM) showed evidence
of spherical particles when dispersions were dried at ∼5 °C
and film formation when dried at room temperature. Many of these polymers
exhibited a reversible lower critical solution temperature (LCST)
in water with a concomitant increase inz-average
diameter for the PDMLA-b-PELA diblock copolymer nanoparticles.