**3. Resins in SLA**

the use of expensive fs pulsed lasers [37]. This process has as of yet not been commercialized,

In bulk lithography, 3D textures can be created by variation of exposure energy. The cure depth, which is a direct function of laser power or scan velocity (i.e. of the applied energy), thereby defines the depth of the features [38]. One can thus see the entire part as only existing of one layer with varying thickness. This eliminates the sometimes abrupt steps in z-direction, which are generated with conventional SLA methods, and vastly speeds up printing. Although this process is not capable of printing structures with overhangs and is limited to geometries thinner than 0.25 mm, it could have potential future applications in high-throughput fabrica-

DLP is a method, which can reach resolutions in the order of 25 μm [7]. Smallest feature sizes of 0.6 μm have also been reported [40], and resins filled with ceramic particles have been printed via DLP with layer heights of 15 μm and with lateral resolutions of 40 μm [18].

In contrast to laser-SLA, the entire cross-section of a layer is illuminated simultaneously by a DLP light engine, as shown in **Figure 4**. The digital micromirror device (DMD) is the key component and functions as a dynamic mask for the DLP process. It is constructed of an array of mirrors, each one representing a single pixel. Individual tilting of every mirror enables fast and reliable switching of pixels [42]. When linked with a computer for image processing, a light source (often LED), and optics, it can project desired cross-sections of light quickly and precisely [42]. The fast switching speed of the DMD is a prerequisite for realizing grayscale illumination, which can be beneficial for precise control over exposure time and by extent

**Figure 4.** Setup of a DLP-SLA printer (A) adapted and redrawn from [22]. Printed polymer structures (B) adapted and reprinted with permission from [41] (Macdonald NP. et al., 3D printed micrometer-scale polymer mounts for single

and very little research is invested in pinpoint solidification-SLA.

*2.2.3. Bulk lithography*

8 3D Printing

tion of microstructures [39].

energy dosage [40].

**2.3. Digital light processing stereolithography**

crystal analysis). Copyright (2017) American Chemical Society.

Photocurable resins for SLA all have the same essential components, as summarized in **Figure 5**. The liquid precursors, which form the network when polymerized, as well as PIs, which start the reaction, are indispensable. In addition, most resin formulations have inert dyes, which absorb incident light and enhance control over the polymerization. Especially when using filled resins, further additives such as diluents, surfactants, or other stabilizers can be present.

#### **3.1. Precursors**

The precursors in SLA are liquid molecules, which can be linked together (i.e. polymerized), after exposure to light to form a solid 3D network. Depending on the future application and desired attributes, a variety of monomers, oligomers, or prepolymers can be utilized.

Especially for complex geometries with undercuts, this cure depth needs to be precisely defined in order to prevent excessive curing in z-direction and loss in feature development [14, 17, 40]. The most commonly used UV absorbers are benzotriazole derivatives [58].

Stereolithography

11

http://dx.doi.org/10.5772/intechopen.78147

Fabrication of metal or ceramic materials via SLA has been implemented by filling resins with powder, printing the parts, and subsequently debinding and sintering the printed specimens [4, 5], as shown in **Figure 6**. During debinding, the organic resin components are removed by pyrolysis. This binder burnout is easier for thin structures with high filler content, as otherwise, defects such as cracks can form [5]. In the subsequent sintering step, the metal or ceramic powder, which remains, is further thermally treated to achieve dense structures [21]. In order to attain geometrically accurate parts, the material specific shrinkage coefficients need to be taken into account, and high filler content is beneficial to reduce shrinkage [60]. Variations of the thermal treatment include implementing an additional drying step prior to debinding to remove solvents or combining debinding and sintering into one single but correspondingly longer thermal process to eliminate potential defect sources during transporta-

Particles smaller than the layer height need to be utilized, and as previously mentioned, maximum particle content is desirable. In highly filled resins with particles in size range of the wavelength of light, scattering is the main interaction mechanism with light and consequently determines cure depth and affects resolution. Reducing the refractive index difference between filler and matrix is a common approach to minimizing scattering [61]. It is noteworthy that composite materials, where the organic component is not removed but retains its matrix function in the final part, have also been manufactured with SLA [3, 62]. By adding (nano)-particles to the SLA resin, mechanical, thermal, optical, or even electrical

**Figure 6.** Scheme of the formation of dense ceramic components from filled resins by SLA, redrawn and adapted from [59].

**3.4. Filled resins**

tion of the fragile brown parts [59].

properties can be further amended [63–65].

**Figure 5.** Resin components in SLA.

Acrylate-based resins are common in the SLA process, as they exhibit high reactivities, which is advantageous for fast building speeds [7]. Different types of acrylates are readily available to tune mechanical properties and thermal resistance for example by altering the number of reactive groups [8] or by employing different oligomers such as urethane acrylates [50]. One disadvantage of acrylate resins is their high-shrinkage during printing, causing potential distortion of the printed part. As a solution, the combination with methacrylates is often implemented [51]. The resin's sensitivity to oxygen, which inhibits the polymerization reaction, is another challenge.

Epoxy systems have a different curing mechanism than acrylates. They are based on cationic rather than radical photopolymerization and need longer reaction times, are inhibited by moisture, but have the advantage of stability against oxygen [52]. Additionally, epoxy resins exhibit significantly lower shrinkage than their acrylate counterparts [53]. In order to exploit the advantages of both alternatives, hybrid systems have been created. Combination of acrylate and epoxy-based resins lead to fast curing, low-shrinkage materials and are nowadays the standard in most commercial systems [54, 55].

#### **3.2. Photoinitiators (PIs)**

The PI is the resin component, which reacts to light. Once irradiated at the correct wavelength, it is excited and can initiate the curing reaction. A suitable PI, depending on the nature of utilized precursor needs to be selected. Type and amount of PI can substantially influence reaction kinetics, necessary light dosage, conversion, cross-linking density, and by extent, mechanical properties of the printed parts [8, 56, 57].

#### **3.3. Absorbers**

Another component that is essential in most SLA processes is a light absorber, which reduces the penetration of light into the resin and limits the depth until, which the resin is cured. Especially for complex geometries with undercuts, this cure depth needs to be precisely defined in order to prevent excessive curing in z-direction and loss in feature development [14, 17, 40]. The most commonly used UV absorbers are benzotriazole derivatives [58].

#### **3.4. Filled resins**

Acrylate-based resins are common in the SLA process, as they exhibit high reactivities, which is advantageous for fast building speeds [7]. Different types of acrylates are readily available to tune mechanical properties and thermal resistance for example by altering the number of reactive groups [8] or by employing different oligomers such as urethane acrylates [50]. One disadvantage of acrylate resins is their high-shrinkage during printing, causing potential distortion of the printed part. As a solution, the combination with methacrylates is often implemented [51]. The resin's sensitivity to oxygen, which inhibits the polymerization reac-

Epoxy systems have a different curing mechanism than acrylates. They are based on cationic rather than radical photopolymerization and need longer reaction times, are inhibited by moisture, but have the advantage of stability against oxygen [52]. Additionally, epoxy resins exhibit significantly lower shrinkage than their acrylate counterparts [53]. In order to exploit the advantages of both alternatives, hybrid systems have been created. Combination of acrylate and epoxy-based resins lead to fast curing, low-shrinkage materials and are nowadays

The PI is the resin component, which reacts to light. Once irradiated at the correct wavelength, it is excited and can initiate the curing reaction. A suitable PI, depending on the nature of utilized precursor needs to be selected. Type and amount of PI can substantially influence reaction kinetics, necessary light dosage, conversion, cross-linking density, and by extent,

Another component that is essential in most SLA processes is a light absorber, which reduces the penetration of light into the resin and limits the depth until, which the resin is cured.

tion, is another challenge.

**Figure 5.** Resin components in SLA.

10 3D Printing

**3.2. Photoinitiators (PIs)**

**3.3. Absorbers**

the standard in most commercial systems [54, 55].

mechanical properties of the printed parts [8, 56, 57].

Fabrication of metal or ceramic materials via SLA has been implemented by filling resins with powder, printing the parts, and subsequently debinding and sintering the printed specimens [4, 5], as shown in **Figure 6**. During debinding, the organic resin components are removed by pyrolysis. This binder burnout is easier for thin structures with high filler content, as otherwise, defects such as cracks can form [5]. In the subsequent sintering step, the metal or ceramic powder, which remains, is further thermally treated to achieve dense structures [21]. In order to attain geometrically accurate parts, the material specific shrinkage coefficients need to be taken into account, and high filler content is beneficial to reduce shrinkage [60]. Variations of the thermal treatment include implementing an additional drying step prior to debinding to remove solvents or combining debinding and sintering into one single but correspondingly longer thermal process to eliminate potential defect sources during transportation of the fragile brown parts [59].

Particles smaller than the layer height need to be utilized, and as previously mentioned, maximum particle content is desirable. In highly filled resins with particles in size range of the wavelength of light, scattering is the main interaction mechanism with light and consequently determines cure depth and affects resolution. Reducing the refractive index difference between filler and matrix is a common approach to minimizing scattering [61]. It is noteworthy that composite materials, where the organic component is not removed but retains its matrix function in the final part, have also been manufactured with SLA [3, 62]. By adding (nano)-particles to the SLA resin, mechanical, thermal, optical, or even electrical properties can be further amended [63–65].

**Figure 6.** Scheme of the formation of dense ceramic components from filled resins by SLA, redrawn and adapted from [59].

#### **3.5. Additives**

A high-volume fraction of solid loading can cause certain disadvantages. Especially for smaller particles with the large surface area, the viscosity of the slurry rises with particle content [4]. This changes the flow behavior of the resin, interferes with coating mechanisms, and increases the mechanical force necessary for the elevation of the building platform in constrained surface setups [19]. Approaches to reduce viscosity include the application of temperature [66], the use of diluents [67], or evoking shear thinning behavior [68].

reduced surface roughness, and faster production times in this application [75]. Channels with dimensions below 100 μm and valves, pumps, as well as multiplexers for mixing [76],

Stereolithography

13

http://dx.doi.org/10.5772/intechopen.78147

Applications in medicine, where patient-specific designs are often necessary to accommodate for individual anatomies, can greatly benefit from AM as well. Some examples are depicted in **Figure 7**. CT or MRI scans can be employed to determine the geometrical specifications, from which devices are then manufactured. Craniofacial implants out of porously structured hydroxyapatite have for example been implanted in patients with large bone defects [80].

In dentistry, CAD modeling has been applied since the 70s in the creation of crowns, which are used to cover a damaged tooth, and dentures, which are removable or fixed devices to replace lost teeth [81]. Now, many AM technologies including SLA can be employed to speed up the process between the acquisition of the geometrical data and implantation of the device into the patient [82]. A second application in healthcare, where AM has become the norm is the manufacturing of hearing aids. SLA can reduce the manufacturing time of these custom-made devices from more than a week to less than a day while also improving wear comfort [83, 84]. Medical applications of SLA are not limited to the fabrication of implants, prostheses, or other medical devices, but drug delivery systems such as micro-needles, capable of administering drugs by painlessly penetrating the skin [78], or 3D printed tablets for individual dosage

**Figure 7.** Top row: CAD model of skull defect (A), SLA fabricated cranial implant (C), and an implant placed into skull model (D), reprinted and modified from [77]. Middle row: SEM images of SLA printed microneedle structures for transdermal drug delivery, modified and reprinted from [78]. Bottom row: SEM images of tissue engineering scaffolds

for bone regeneration by SLA, modified and reprinted from [79] by permission of Springer Nature.

can be fabricated rapidly and easily.

Rheological additives and stabilizers can increase solid loading and are necessary for extended shelf-life of slurries as well as for stability during longer printing jobs [68]. Agglomeration and sedimentation of particles need to be avoided to ensure continuous, homogeneous ceramic or metal powder distribution. To that end, dispersants such as oligomeric surfactants [69], long chained acids like oleic acid [70], or phosphine oxides with aliphatic chains [71] have been used.

#### **3.6. Post-processing**

After removal of the built part from the platform, any support structures that had been necessary for the printing process need to be cut from the green part. Cleaning in suitable solvents and drying of the structure is often followed by sanding of support residues. Post-curing in a UV chamber can be implemented to complete conversion of the polymerization reaction and thereby attain improved mechanical properties [72]. In the case of filled resins, debinding and sintering are the final post-processing steps.


**Table A9. Positive ideal alternative** *A k*+ *i* **and negative ideal alternative** *A k*− *i*.

**Table A10. Alternatives' positive ideal solution distance** *d k*+ *i*

.

**Table A11. Alternatives' negative ideal solution distance** *d k*− *i*.

### **References**

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

### *Article*


*Edited by Manar El-Sayed Abdel-Raouf*

Petroleum "black gold" is the most important nonrenewable source of energy. It is a complex mixture of different phases and components. Refining it provides a vast number of organic compounds, all of them of which are used to produce petroleum based products for numerous applications, from industry to medicine, from clothing to food industries. We can find petroleum based products all around us. This book deals with some important topics related to petroleum such as its chemical composition and stability. It is well-known that the chemical composition of crude oil differs according to the site of production, and its grade varies from waxy to asphaltenic crude. Both of them are refined to produce different products. The stability of crude oil on aging and transportation is governed by several factors and these factors are included within this book. Some new technologies for petroleum characterization are also introduced. This book is aimed at researchers, chemical engineers and people working within the petroleum industry.

ISBN 978-953-51-0220-5

Crude Oil Emulsions - Composition Stability and Characterization

Photo by Shebeko / Depositphotos

## Crude Oil Emulsions Composition Stability and Characterization

*Edited by Manar El-Sayed Abdel-Raouf*

**CRUDE OIL EMULSIONS –**

**COMPOSITION STABILITY**

**AND CHARACTERIZATION**

Edited by **Manar El-Sayed Abdel-Raouf**

**INTECHOPEN.COM**


**4. Completely Positive Instrument**

In this section, we analyze the concept of CP instrument in the C∗-algebraic setting. In previous investigations [17–20], it has been examined in the von Neumann algebraic formulation of quantum theory. The generalization to C∗-algebra is realized in terms of central subspaces of the dual of a C∗-algebra. Our approach enables us to unify the measurement theory with sector theory.


*Review* **Zinc (II) and AIEgens: The "Clip Approach" for a Novel Fluorophore Family. A Review**

**Rosita Diana and Barbara Panunzi \***

Department of Agricultural Sciences, University of Naples Federico II, 80055 Portici, Italy<EMAIL_ADDRESS>**\*** Correspondence<EMAIL_ADDRESS>Tel.: +39-081-674-170

**Abstract:** Aggregation-induced emission (AIE) compounds display a photophysical phenomenon in which the aggregate state exhibits stronger emission than the isolated units. The common term of "AIEgens" was coined to describe compounds undergoing the AIE effect. Due to the recent interest in AIEgens, the search for novel hybrid organic–inorganic compounds with unique luminescence properties in the aggregate phase is a relevant goal. In this perspective, the abundant, inexpensive, and nontoxic d10 zinc cation offers unique opportunities for building AIE active fluorophores, sensing probes, and bioimaging tools. Considering the novelty of the topic, relevant examples collected in the last 5 years (2016–2021) through scientific production can be considered fully representative of the state-of-the-art. Starting from the simple phenomenological approach and considering different typological and chemical units and structures, we focused on zinc-based AIEgens offering synthetic novelty, research completeness, and relevant applications. A special section was devoted to Zn(II) based AIEgens for living cell imaging as the novel technological frontier in biology and medicine.

**Keywords:** AIE; zinc complex; fluorescence

#### - **-**

**Citation:** Diana, R.; Panunzi, B. Zinc (II) and AIEgens: The "Clip Approach" for a Novel Fluorophore Family. A Review. *Molecules* **2021**, *26*, 4176. https://doi.org/10.3390/ molecules26144176

Academic Editors: Jorge Bañuelos Prieto and Ugo Caruso

Received: 16 June 2021 Accepted: 6 July 2021 Published: 9 July 2021

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).


**3.2 The cross-linking and pyrolysis of polysilanes with functional groups**

The mass retaining ratio of EPS1 was much higher than that of EPS2 (Table 7), and was close to that of EPS1/DVB (1/0.5). It could be inferred that the double bonds on EPS1 had played important role in the cross-linking processes and were the cause of high mass retaining ratio. The ceramic yields of self-cross linking samples were dramatically higher, compared with specimens having DVB as curing agent. DVB might form inhomogeneous structure during curing process, leading to lower ceramic yield26. Therefore, it is not necessary to add curing agent to polysilane with double bonds, which is on its own a good ceramic precursor. The Zr-containing EPS3 also had a high mass retaining ratio and a moderate ceramic yield.

DVB: Divinylbenzene , as curing agent.

Table 7. Mass retaining ratio and Ceramic yield of EPS1, EPS2 and EPS3

Electropolymerization of Polysilanes with Functional Groups 17

modified with SiC ceramic27. The introduction of SiC can be achieved by the chemical vapor infiltration (CVI) and the polymer infiltration and pyrolysis (PIP)28. PIP has aroused much interest due to its low manufacturing temperature, ability for the design of precursor molecules, simplicity of formation and feasibility of fabricating complex components. The main precursors for SiC at present are polycarbosilane and polysilane (PS)4. The C/C–SiC composites were manufactured using PS with double bonds by the PIP technique9. The C/C-ZrC-SiC composites were prepared using Zr-containing polysilane. The ablation

The used C/C composites with a density of 1.29 g/cm3 were made by CVI of bulk needled carbon felt and temperature treatment at 2 300 ℃. The C/C–SiC composites and C/C-ZrC-SiC composites were densified by the following procedure: C/C composites → vacuum + pressure infiltration of precursor → cross-linking → pyrolysis → sintering. The process was repeated several times. The maximum density of the obtained C/C–SiC and C/C-ZrC-SiC

The specimens, with a size of ø30 mm×10 mm, were flushed vertically with a H2–O2 torch flame. The inner diameter of the nozzle tip was 4.68 mm. The distance between the nozzle tip and specimen surface was 15.8 mm. The pressure and flux of oxygen were 1.55 MPa and 2.1 L/min, and for hydrogen, they were 0.18 MPa and 1.68 L/min, respectively. The ablation

The thickness of the specimen before ablation (d1) was measured with a micrometer (precision 0.01 mm), and the mass (m1) was measured with an analytical balance (precision 0.1 mg). After ablation, the thickness at the lowest point (d2) and mass (m2) were measured. For the ablation time of t, the linear ablation rate was calculated by (d1-d2)/t, and the mass

1.3 1.4 1.5 1.6 1.7 1.8

The ablation test results are depicted in Fig.12 and Fig.13, which show that the linear and mass ablation rate of the C/C–SiC and C/C-ZrC-SiC were lower than that of the C/C composites at the same density. With the increase of infiltration times, the density of C/C– SiC specimens increased, and the ablation rate decreased. The linear ablation rates of the 1.75 g/cm3 C/C–SiC and 1.69 g/cm3 C/C-ZrC-SiC specimen were 21.7% and 20.6% those of

ρ(**g.cm-3**)

 C/C 180S C/C-ZrC-SiC 180S C/C-SiC 180S

behavior of the C/C–SiC composites and C/C-ZrC-SiC composites were measured.

composites were 1.75 g/cm3 and 1.69 g/cm3, respectively.

ablation rate was calculated by (m1-m2)/t.

**Linear ablation rates**(**mm.s-1**

Fig. 12. Linear ablation rate of specimens

)

0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035

time was 180 s.

XRD pattern of the pyrolyzed product of EPS1 at 1300℃(Fig. 10) shows broad peaks of β-SiC (2θ =35.6°,60°,71.8°). That of EPS3 (Figure 11) shows the existence of β-SiC, ZrC, Si and SiO2.

Fig. 10. XRD spectrum of EPS1's pyrolyzed product

Fig. 11. XRD pattern of ceramic from EPS3

#### **3.3 Improvement of the anti-oxidative ablation property of C/C composites by using polysilanes with functional groups**

The poor oxidation resistance of C/C composites restricts its usage in oxidized environments. To improve its oxidative ablation resistance, the matrix of C/C composites is

XRD pattern of the pyrolyzed product of EPS1 at 1300℃(Fig. 10) shows broad peaks of β-SiC (2θ =35.6°,60°,71.8°). That of EPS3 (Figure 11) shows the existence of β-SiC, ZrC, Si and SiO2.

> 20 40 60 80 100 Deg./2θ

30 40 50 60 70 80

**3.3 Improvement of the anti-oxidative ablation property of C/C composites by using**

The poor oxidation resistance of C/C composites restricts its usage in oxidized environments. To improve its oxidative ablation resistance, the matrix of C/C composites is

ZrC

Si Si

SiC

2θ(。)

SiO2

SiC

Fig. 10. XRD spectrum of EPS1's pyrolyzed product

SiC

ZrC

Fig. 11. XRD pattern of ceramic from EPS3

**polysilanes with functional groups**

SiO2

modified with SiC ceramic27. The introduction of SiC can be achieved by the chemical vapor infiltration (CVI) and the polymer infiltration and pyrolysis (PIP)28. PIP has aroused much interest due to its low manufacturing temperature, ability for the design of precursor molecules, simplicity of formation and feasibility of fabricating complex components. The main precursors for SiC at present are polycarbosilane and polysilane (PS)4. The C/C–SiC composites were manufactured using PS with double bonds by the PIP technique9. The C/C-ZrC-SiC composites were prepared using Zr-containing polysilane. The ablation behavior of the C/C–SiC composites and C/C-ZrC-SiC composites were measured.

The used C/C composites with a density of 1.29 g/cm3 were made by CVI of bulk needled carbon felt and temperature treatment at 2 300 ℃. The C/C–SiC composites and C/C-ZrC-SiC composites were densified by the following procedure: C/C composites → vacuum + pressure infiltration of precursor → cross-linking → pyrolysis → sintering. The process was repeated several times. The maximum density of the obtained C/C–SiC and C/C-ZrC-SiC composites were 1.75 g/cm3 and 1.69 g/cm3, respectively.

The specimens, with a size of ø30 mm×10 mm, were flushed vertically with a H2–O2 torch flame. The inner diameter of the nozzle tip was 4.68 mm. The distance between the nozzle tip and specimen surface was 15.8 mm. The pressure and flux of oxygen were 1.55 MPa and 2.1 L/min, and for hydrogen, they were 0.18 MPa and 1.68 L/min, respectively. The ablation time was 180 s.

The thickness of the specimen before ablation (d1) was measured with a micrometer (precision 0.01 mm), and the mass (m1) was measured with an analytical balance (precision 0.1 mg). After ablation, the thickness at the lowest point (d2) and mass (m2) were measured. For the ablation time of t, the linear ablation rate was calculated by (d1-d2)/t, and the mass ablation rate was calculated by (m1-m2)/t.

Fig. 12. Linear ablation rate of specimens

The ablation test results are depicted in Fig.12 and Fig.13, which show that the linear and mass ablation rate of the C/C–SiC and C/C-ZrC-SiC were lower than that of the C/C composites at the same density. With the increase of infiltration times, the density of C/C– SiC specimens increased, and the ablation rate decreased. The linear ablation rates of the 1.75 g/cm3 C/C–SiC and 1.69 g/cm3 C/C-ZrC-SiC specimen were 21.7% and 20.6% those of

Electropolymerization of Polysilanes with Functional Groups 19

[5] Subramanian, K., A review of electrosynthesis of polysilane. *Journal of Macromolecular Science-Reviews in Macromolecular Chemistry and Physics* 1998, C38, (4), 637-650. [6] Kashimura, S.; Ishifune, M.; Yamashita, N.; Bu, H. B.; Takebayashi, M.; Kitajima, S.;

magnesium electrodes. *Journal of Organic Chemistry* 1999, 64, (18), 6615-6621. [7] Elangovan, M.; Muthukumaran, A.; Kulandainathan, M. A., Novel electrochemical

[8] Wu, S.; Chen, L.; Zhang, F.-j., Polysilane with double bonds by electrochemical synthesis.

[9] Wu, S.; Chen, L.; Qian, L.; Zhang, J.; Pan, J.; Zhou, C.; Ren, M.; Sun, J., Ablation

[10] Cao, S.-w.; Xie, Z.-f.; Wang, J.; Wang, H.; Tang, Y.; Li, W.-h., Research progress in

[11] Chen, Y.; Du, L., *Organic Quantitative Microanalysis*. Science Press, China: Beijing,

[12] Gozzi, M.; Yoshida, I., Structural evolution of a poly(methylsilane)/tetra-allylsilane mixture into silicon carbide. *European Polymer Journal* 1997, 1301-1306. [13] Yang, G.; Gao, S.; Gu, Q.; Xu, N., Purification of carbosilane dendrimers by column chromatography. *Nanjing Gongye Daxue Xuebao, Ziran Kexueban* 2010, 32, (1), 19-22.

[14] Vermeulen, L. A.; Smith, K.; Wang, J. B., Electrochemical polymerization of

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[17] Colombo, P.; Mera, G.; Riedel, R.; Soraru, G. D., Polymer-Derived Ceramics: 40 Years

[18] Yamaoka, H.; Ishikawa, T.; Kumagawa, K., Excellent heat resistance of Si-Zr-C-O fibre.

[19] Li, X.; Edirisinghe, M. J., Evolution of the ceramic structure during thermal degradation of a Si-Al-C-O precursor. *Chemistry of Materials* 2004, 16, (6), 1111-19. [20] Amoros, P.; Beltran, D.; Guillem, C.; Latorre, J., Synthesis and characterization of

[21] Xing, X.; Liu, L.; Gou, Y.; Li, X., Research progress of polymethylsilane in precursor of

[22] Shibuya, M.; Yamamura, T., Characteristics of a continuous Si-Ti-C-O fibre with low

silicon carbide ceramics. *Guisuanyan Xuebao* 2009, 37, (5), 898-904.

alkyltrichlorosilane monomers to form branched Si backbone polymers.

by Reductive Coupling of Disubstituted Dichlorosilanes with Alkali Metals.

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the 1.78 g/cm3 C/C specimen, respectively. And the mass ablation rates of the 1.75 g/cm3 C/C–SiC and 1.69 g/cm3 C/C-ZrC-SiC specimen were 78.6% and 31.6% those of the 1.78 g/cm3 C/C specimen, respectively. Therefore, introduction of SiC into C/C composite greatly improved its oxidative ablation-resistive property, and the adulteration of Zr element enhances the effect even more. It is worthwhile to investigate the impact of attaching refractory metals, such as Ta, Zr, Hf, Th, et al. solely or combinatorially to polysilanes on the anti-oxidative ablation property of the C/C composites.

Fig. 13. Mass ablation rate of specimens

### **4. Conclusions**

The electroreduction MeSiCl3 and Allyl chloride monomers carried out with Mg electrodes in a single compartment cell gave polysilane with double bonds. The preferred MeSiCl3/Allyl chloride ratio was 3:1. The molecular weight and yield of the products were affected by the concentration of monomer, the amount of electricity, the electrode's interval time and concentration of supporting electrolyte. By introducing cyclopendienyl ligands as side groups of polysilanes, the polysilanes with refractory metals were obtained by the combination of Cp with the metal elements. The synthesized polysilanes with self-curable ability and high ceramic yields are excellent ceramic precursors.

### **5. References**

the 1.78 g/cm3 C/C specimen, respectively. And the mass ablation rates of the 1.75 g/cm3 C/C–SiC and 1.69 g/cm3 C/C-ZrC-SiC specimen were 78.6% and 31.6% those of the 1.78 g/cm3 C/C specimen, respectively. Therefore, introduction of SiC into C/C composite greatly improved its oxidative ablation-resistive property, and the adulteration of Zr element enhances the effect even more. It is worthwhile to investigate the impact of attaching refractory metals, such as Ta, Zr, Hf, Th, et al. solely or combinatorially to

1.3 1.4 1.5 1.6 1.7 1.8

 C/C 180S C/C-ZrC-SiC 180S C/C-SiC 180S

ρ(**g.cm-3** )

The electroreduction MeSiCl3 and Allyl chloride monomers carried out with Mg electrodes in a single compartment cell gave polysilane with double bonds. The preferred MeSiCl3/Allyl chloride ratio was 3:1. The molecular weight and yield of the products were affected by the concentration of monomer, the amount of electricity, the electrode's interval time and concentration of supporting electrolyte. By introducing cyclopendienyl ligands as side groups of polysilanes, the polysilanes with refractory metals were obtained by the combination of Cp with the metal elements. The synthesized polysilanes with self-curable

[1] Hayase, S., Polysilanes for semiconductor fabrication. *Progress in Polymer Science* 2003, 28,

[2] Roewer, G.; Herzog, U.; Trommer, K.; Muller, E.; Fruhauf, S., Silicon carbide - A survey

[4] Chandrasekhar, V., Polysilanes and Other Silicon-Containing Polymers. In *Inorganic and Organometallic Polymers*, Springer Berlin Heidelberg: 2005; pp 249-292.

[3] Hayase, S., Polysilanes with functional groups. *Endeavour* 1995, 19, (3), 125-131.

of synthetic approaches, properties and applications. In *High Performance Non-Oxide*

polysilanes on the anti-oxidative ablation property of the C/C composites.

0.5

ability and high ceramic yields are excellent ceramic precursors.

*Ceramics I*, 2002; Vol. 101, pp 59-135.

1.0

1.5

2.0

**Mass ablation rates**(**mg.s-1**

Fig. 13. Mass ablation rate of specimens

**4. Conclusions**

**5. References**

(3), 359-381.

)

2.5

3.0

3.5

**2**

 *Egypt*

**Electropolymerization of Some Ortho-**

**from Aqueous Acidic Solution; Kinetics,**

S.M. Sayyah\*, A.B. Khaliel, R.E. Azooz and F. Mohamed *Polymer Research Laboratory, Chemistry Department, Faculty of Science,*

*Beni-Suef University 62514, Beni-Suef City,*

**Mechanism, Electrochemical Studies and Characterization of the Polymer Obtained**

**Substituted Phenol Derivatives on Pt-Electrode**

One of the promising methods for waste water remediation is The electrochemical oxidation of hazardous organic species [Fleszar & Jolanta, *1985;* Comninellis, 1994].  The quantitation of phenolic compounds in environmental, industrial and food samples is currently of great interest, which can be found in soils and groundwater [Wang et al., 1998]. Also, these compounds are important synthesis intermediates in chemical industry such as resins, preservatives, pesticides, etc. Another, the main sources of phenolic waste are in glass fiber insulation manufacture on petroleum refineries. Phenol and substituted phenolic compounds such as catechol, chlorophenol are hydroquinones and discharged in the effluent from a number of chemical process industries. Today, these compounds are found in relatively high amount in domestic and industrial wastewater, discharged mainly from the mechanical industries. Many treatment technologies are in use

The electrooxidation of phenolic compounds can be occurs as follows: in the first step of electrooxidation of phenols, phenoxy radicals are generated, then these species can be either oxidized further or be coupled, forming ether and oligomeric or polymeric compounds [Wang et al ,1991; Iotov, & Kalcheva, 1998]. Electropolymerization of phenol beings with the formation of the phenoxy radical, or it can react with a molecule of phenol to give predominantly a para-linked dimeric radical. This radical may be further oxidized to form a neutral dimmer or it may attach another molecule. The dimer may be further oxidized create oligomers to polymers. Formation of the insoluble polyphenol results in deactivation of electrode surface. The relative rates of the two pathways (polymerization and forming quinonic structure) depend on the phenols concentration, the nature of electrode, pH, solvent, additives, electrode potential and current density [Gattrell & Kirk,1993]. Electropolymerization of phenols occur on different electrodes, such as Fe, Cu, Ni, Ti, Au, Pt

or have been proposed for phenol recovery or destruction.

**1. Introduction**


**4. High-grade transformation does not confer** *Hp***-independence of gastric lymphoma**

It was previously believed that the transformation of MALT lymphoma into high-grade MALT lymphoma, is associated with the acquisition of *Hp*independence (lack of CR of tumors after HPE); high-grade MALT lymphoma is thus considered as a *Hp*-independent tumor that is non-responsive to antibiotics (**Figure 1**) [18–20, 56]. Clinicians who administer first-line HPE to treat patients with high-grade gastric MALT lymphoma do so as they may regard MALT lymphoma as similar to low-grade MALT lymphoma that is highly responsive to HPE. Thus, to avoid such a confusion, Harris et al. in a 1999 WHO classification advised that high-grade MALT lymphoma should be renamed as DLBCL with histologic evidence of MALT (DLBCL[MALT]), and not as transformed high-grade MALT lymphoma [57]. In 2008, the WHO lymphoma classification advocated that histological manifestations of gastric lymphoma that display large-cell B-cell transformation in the MALT lymphoma background should be classified as DLBCLs rather than as high-grade transformed MALT lymphomas [5]. In this milieu, the presence of large B cells comprising LELs does not alter the pathological diagnosis of DLBCL [5, 6]. Regardless of this, the existence of complementary MALT lymphoma components in DLBCL should be appraised consistently [4, 5, 58].

However, two independent prospective studies and one retrospective study have revealed that a certain proportion of early-stage *Hp*-positive gastric DLBCL(MALT) patients were still responsive to first-line HPE, and thus achieved CR and subsequent long-term remission [21–24]. In the first prospective study, Chen et al. (Taiwan study group) demonstrated that 10 (62.5%) of 15 patients with early-stage gastric DLBCL(MALT) achieved CR after receiving first-line HPE, and remained lymphoma-free during a long-term follow-up [21]. In another prospective study assessing the association between clinicopathological features and tumor response

#### **Figure 1.**

*Gastric diffuse large B-cell lymphoma as well as gastric mucosa-associated lymphoid tissue (MALT) lymphoma are* Helicobacter pylori*-dependent, and are cured by first-line Hp eradication therapy (HPE). In contrast to the classic concept that gastric diffuse large B-cell lymphomas (DLBCLs) with and without histological evidence of MALT lymphoma are not responsive to HPE, several evidences demonstrated that*  Hp*-related gastric lymphoma does not involve loss of* Hp*-dependence and is responsive to HPE, indicating that the spectrum of* Hp*-related gastric lymphoma is much wider than was originally thought.*

to HPE in gastric MALT lymphoma and DLBCL(MALT), Nakamura et al. reported that five (50%) of 10 gastric DLBCL(MLAT) patients had CR, whereas 4/6 with mucosa and submucosa involvement and 1/4 patients with tumor involvement in the muscularis propria were *Hp*-dependent [22]. Of these, five *Hp*-dependent patients were still free of lymphoma after a median follow-up of five years [22]. Mongnar et al. retrospectively analyzed eight patients with gastric DLBCL(MALT) who initially received HPE, of whom seven patients had CR [23]. Among these *Hp*-dependent patients, four patients did not receive further treatment, whereas one patient developed recurrence at six months after completing HPE, and another two patients underwent surgery later (one patient received chemotherapy because of residual MALT lymphoma in the surgical specimen) [23].

In 2005, Chen et al. reported the clinical outcome of a prospective study using first-line HPE for treating 24 patients with gastric DLBCL(MALT) and 36 patients with gastric MALT lymphoma, and demonstrated that 24 (80%) of 30 patients with MALT lymphoma and 14 (63.6%) of 22 patients with DLBCL(MALT) achieved CR after successful HPE [24]. The median time to CR after the completion of HPE for *Hp*-dependent patients was six months for DLBCL(MALT), and 10 months for MALT lymphoma [24]. Interestingly, after a median long-term follow-up (MALT lymphoma, 70 months; DLBCL[MALT], 56 months) for these *Hp*-dependent patients, the tumor did not recur in the DLBCL(MALT) case, but recurred in three cases of MALT lymphoma [24]. Regarding the depth of tumor infiltration associated with tumors responsive to HPE, the CR rate was 80% (8/10) for tumors limited to the mucosa or submucosa, and 29.4% (5/17) for tumors invading the muscularis propria or beyond (P = 0.018) [24].

In 2008, Cavanna et al. [59] reviewed the anecdotal cases series reporting the CR after antibiotic treatment for gastric DLBCL(MALT) and the results of HPE for patients with gastric DLBCL(MALT) obtained from Chen et al. [21, 24], Nakamura et al. [22], Morgan et al. [23], Hiyama et al. [60], and Alpen et al. [61]. Cavanna et al. showed that 42 (68.9%) of 61 cases of gastric DLBCL(MALT) responded completely to antibiotics eradicating *Hp*; most patients in this study presented with stage IE (30 cases), with tumor invasion to the mucosa or submucosa (21 of 33 cases were evaluable) [59]. However, age, sex, and tumor location (proximal or distal components) did not predict the response of tumors to HPE [59]. Although depth of invasion and stage of gastric DLBCL(MALT) were closely associated with

*Revisiting the Full Spectrum of* Helicobacter pylori*-Related Gastric Lymphoma DOI: http://dx.doi.org/10.5772/intechopen.97424*

*Hp*-independence, there were a few cases of stage IIE1 (perigastric lymph node involvement) tumors that were dependent on *Hp* and achieved CR after HPE [59]. Zullo et al. analyzed the pooled data obtained from 1271 patients with gastric MALT lymphoma or DLBCL(MALT) through 34 studies exploring the treatment efficacy of first-line HPE, and revealed that a *Hp* eradication rate of 91% can be achieved using dual therapy for 14 days or triple therapy for seven to 14 days [62]. In their analyses, the CR rate was 78.5% for MALT lymphoma patients (n = 1215), and 62% for DLBCL(MALT) patients (n = 52) [62]. In the report of therapeutic efficacies of first-line HPE in gastric DLBCL(MALT) patients by Kuo et al. [26], the CR rate was 56.3% (18/32) with a median interval to CR of 5.0 months; the CR rate was significantly associated with the tumor extent (mucosa/submucosa vs. beyond: 80% [8/10] vs. 29.4% [5/17], P = 0.018) [26].

It should be noted that if patients with gastric DLBCL(MALT) do not respond well to antibiotic treatment, the tumor may rapidly progress and cause potential morbidities in these patients. However, for *Hp*-independent gastric DLBCL(MALT) patients, subsequent systemic chemotherapy could result in CR and let patients remain disease-free during long-term follow-up [21–25, 63]; this implies that a delay in the administration of systemic chemotherapy to 6–8 weeks after HPE with antibiotics is unlikely to influence the response of these tumors to conventional immunochemotherapy. These findings may support the contention that

#### **Figure 2.**

*Changes of endoscopic features in an example of stage IE* Helicobacter pylori *(*Hp*)-dependent localized gastric diffuse large B-cell lymphoma (DLBCL) with mucosa-associated lymphoid tissue (MALT) (DLBCL[MALT]) before and after completion of Hp eradication therapy (HPE) (A) Endoscopy shows several ulcerative mass lesions with nodular and irregular margins at the antrum of a 74-year-old man before HPE (Histopathology disclosed DLBCL[MALT], DLBCL-predominant). (B) Computed tomography (CT) shows moderate wall thickening (white arrow) in the gastric antrum but no enlargement of perigastric lymph nodes in the same case A. (C) One month after the completion of HPE, endoscopy shows two partially regressed ulcerative masses at the gastric angle in the same case A (D) Four months after completion of HPE, complete remission was achieved in the same case A. Right bottom, CT shows no gastric wall thickening (white arrow).*  Hp*,* Helicobacter pylori*; HPE, Hp eradication therapy; DLBCL, diffuse large B-cell lymphoma; MALT, mucosa-associated lymphoid tissue; CT, computed tomography; CR, complete remission.*

#### *Revisiting the Full Spectrum of* Helicobacter pylori*-Related Gastric Lymphoma DOI: http://dx.doi.org/10.5772/intechopen.97424*

first-line HPE should be administered to additional populations of stage IIE1 gastric DLBCL(MALT) patients. This concept is further supported by a prospective clinical trial (T3206) designed by the TCOG in evaluating the treatment efficacy of first-line HPE consisting of omeprazole, amoxicillin, and clarithromycin for 14 days in patients with *Hp*-positive stage IE or stage IIE1 MALT lymphoma, and DLBCL(MALT) of the stomach [25]. This trial revealed that 8 (80%) of 10 patients with DLBCL(MALT) and 26 (76.5%) of 36 patients with MALT lymphoma achieved CR (**Figure 2**); the CR rate was not different between stage IE (75%) and stage IIE1 (66.7%) [25]. After a median follow-up of 59 months, all eight *Hp*-dependent DLBCL(MALT) patients remained lymphoma-free, whereas three (7.7%) of the 26 *Hp*-dependent MALT lymphoma patients relapsed after a median follow-up of 82 months [25]. Notably, tumor invasions to the perigastric lymph nodes are not exclusive to *Hp*-dependent cases, suggesting that pivotal mechanisms exist in these tumors; this is because lymphoma cells of the perigastric lymph nodes communicate indirectly with the *Hp* bacteria.

Taken together, these findings show that the tumor remission rates after HPE are identical between MALT lymphoma and DLBCL(MALT) of the stomach (**Table 1**), which overthrows the classical concept that the transformation of MALT lymphoma into high-grade DLBCL(MALT) is associated with the acquisition of *Hp*-independence and thus DLBCL(MALT) is unlikely to respond to HPE. These clinical discoveries are in line with previous molecular studies showing the difference in clonalities between MALT lymphoma components and DLBCL components of the same stomach [64–66]. Kuo et al. compared the patterns of *IgH* rearrangement between DLBCL and MALT lymphoma components of the same gastric DLBCL(MALT) patients receiving HPE, and revealed that different clonal origins of the two co-existing components contributed to the differential response to HPE [67]. In the long-term follow-up of gastric MALT lymphoma without remission, Liu et al. showed that the frequency of development of DLBCL from MALT lymphoma was less than 2%, suggesting rare high-grade transformation in gastric MALT lymphoma [68]. These results indicate that some DLBCL components may evolve independently from their co-existing MALT lymphoma counterparts in gastric DLBCL(MALT). Overall, with reference to clinical impact, first-line HPE resulting in a durable CR rate of approximately 60% has revolutionized the treatment of gastric DLBCL(MALT), and has helped 60% of DLBCL(MALT) patients to avoid the risks of systemic chemotherapy (**Table 1**). With reference to molecular impact, the high-grade transformation of gastric MALT lymphoma does not confer *Hp*-independence to the tumor cells (**Figure 1**); this finding will eventually lead to the revision of the current lymphoma classification, such as the Revised European American Lymphoma Classification (REAL)/WHO. In the REAL/WHO, high-grade gastric MALT lymphoma is classified as DLBCL with histological evidence of MALT (DLBCL[MALT]), and is recommended to be treated as common DLBCL [3, 5, 57].