Silylated monomers

The role of silyl groups in condensation polymerization is different from that in GTP. The use of silylated monomers in condensation polymerization was studied first by Klebe [90-92] in 1964. N-trimethylsilyl-substi-... 

The use of silylated monomers is an interesting alternative method of aromatic polyester synthesis since the silylated gaseous by-products cannot participate in the reverse reaction, shifting polyesterification toward polymer formation. Reactions between silyl esters and acetates (Scheme 2.23) and reactions between silyl ethers and acid chlorides (Scheme 2.24) have been applied to the synthesis of linear265-267 and hyperbranched wholly aromatic polyesters202,268 269 (see Section 2.4.5.2.2). 

Silylated diamines, 156, 187-188 Silylated monomers, 72 Silylation, distillation and, 338 6NT6 alternating polyesteramide, synthesizing, 189-190 6,6 -linked polymers, 480 Size exclusion chromatography (SEC) analyses, 90, 490 Slabstock foam, 233-234 Slow monomer addition, 57 Small-angle neutron scattering (SANS), 282... 

Desilylation model studies were carried out on both the silylated monomer and polymer to develop suitable reaction conditions. The desilylation of the TMSEMA was instantaneous as indicated with GC by the increase in the retention time of the monomer. The desilylation the PTMSEMA was equally facile as determined by NMR spectroscopy Figure 1 shows the disappearance of the -Si(CH3)3 resonance at 0.1 ppm and the appearance of the -OH resonance at 3.3 ppm without detectible ester hydrolysis even after four days. 

In addition to providing many new precursors to functionalized poly(alkyl/arylphosphazenes), the deprotonation/substitution reactions of these N-silylphosphoranimines serve as useful models for similar chemistry that can be carried out on the preformed polymers. New reactions and experimentation with reaction conditions can first be tried with monomers before being applied to the more difficult to prepare polymeric substrates. A considerable amount of preliminary work [e.g., with the silylated monomers (z z) and polymers (2 o) has demonstrated the feasibility of this model system approach. 

Open tubular CEC-MS (OT-CEC-MS) bearing positively charged alkylamino silyl monomers... 

TABLE 1. Summary of M s obtained using silyl monomers after 10 minntes of polymerization with ethylene and propylene. 

The HOSu-containing polymer 85 has been obtained by ROMP of O-silylated oxanorbornene monomer 84 using Grubbs catalyst and terminating the reaction with ethyl vinyl ether, followed by further desilylation, as the non-silylated monomer did not undergo the ROMP process (Scheme 7.27) [108]. The final polymer 85 was... 

Copolymers of 4-silyloxy-a-methylstyrene or silyl methacrylate with meth-acrylonitrile were prepared by radical copolymerization of silyl monomer or by silylation of acidic copolymer and evaluated as 157 nm positive bilayer resists [437]. 

The polymeric silica materials derived from silylated aryl iodides have been prepared via sol-gel processes, either by the hydrolytic polycondensation of a bis-silylated monomer or by the co-gelification of a monosilylated precursor with tetraethyl orthosilicate [113]. These silica-supported aryl iodides have been successfully applied as supported catalysts in the a-tosyloxylation of aliphatic ketones in the presence of m-chloroperbenzoic acid as an oxidant, with the corresponding a-tosyloxyketones obtained in moderate to good isolated yields. The supported catalysts can be recycled by a simple filtration [113]. 

The efficiencies of imprinted polymers used as stationary phases in chromatography are often greatly improved when used in capillary electro chromatography columns. These polymers are usually produced in the column, by attaching the imprinted polymer to the fused silica wall [27-30]. This is often done by derivatizing the column wall with a silylated monomer such as [3-(methacryloyloxy)propylj-trimethoxysilane, or adsorbing an initiator to the surface [31-34] as illustrated in Fig. 6. 

Khanna et al. prepared a series of fluorinated hydroxypolyamides (HPAs) without using any silylated monomer. They prepared the PBO by using 2,2-bis(3-amino-4-hydroxyphenyl)-1,1,1,3,3,3-hexa-fluoropropane and different aromatic dicarboxylic acids. These HPAs were soluble in a variety of solvents, and the TgS were found in the range of 235-280 °C. Finally, these polymers were converted into... 

Finally, we will concentrate on the chemical reactivity of silyl derivatives of thiophene. The oxidative polymerization of various silyl monomers lead to polythiophene. The evaluation of this new polymerization reaction implies a precise characterization of the produced conjugated materials. Knowledge and the control of the pertinent parameters which direct the properties of the conjugated systems are essential. Also required is the development of methods which allow a precise characterization of the samples. The role of vibrational infrared and Raman spectroscopy is of fundamental importance in this field. Optical spectroscopy is one of the few tools for unravelling the structure of these materials and understanding their properties. First, new criteria based on infrared, Raman and photoluminescence spectroscopy which allow precise estimates of the conjugation properties will be reported. Then the synthesis and characterization of polythiophene samples arising from the oxidative polymerization of silyl thiophene will be presented. 

Improvement in the efficiency of organic light-emitting diodes made of conjugated oligomers and polymers is a good example of the application of silylated monomers and emphasizes the interest in... 

In conclusion, comparison of photoluminescence bands performed on different samples gives another method to distinguish between different samples, and to evaluate the value and polydispersity of the conjugation length. In the following, a significant dependence of photoluminescence on the structural order in polythiophenes synthesized from silylated monomers will be established. 

Table 14.6. In contrast, the use of bis silylated monomer leads to a free-standing film with a good conductivity (Table 14.6). Moreover, the voltam-mogram of the latter shows similarities with that of polythiophene rather with the voltammogram of poly(bi)diiophene... 

Since the original report of Lemaire and Roncali several authors have reported the preparation of polythiophene films from silylated monomers (Scheme... 

It is worth noting that the j -eflfect of silicon can also enhance a side-reaction such as protodesilylation of silylated thiophene. As noted in references [10] and [13], electropolymerization of silyl monomers must be performed in an anhydrous medium. Moreover, the... 

The effect of the use of silylmonomers on the structural properties of polythiophene has been established on the basis of Raman and photoluminescence criteria [10,92-4]. In the following two sub-sections, we report the characterizations and data obtained on polythiophenes prepared from electropolymerization and chemical oxidation of a-silylated monomers (Scheme 14.32 and Table 14.10. We are going to focus in particular on experimental data which allow us to stress the role of SiMca groups. 

Polythiophenes have also been prepared by chemical oxidation of a-silylated thiophene and compared to samples prepared from hydrogenated thiophenes [20]. In this section, we focus on the improvement in the structural order and conjugation in polythiophenes resulting from the use of silylated monomers, and on the effect of a thermal treatment on structural order and conjugation of polythiophene. 

Figure 14.17. Raman spectra of electrochemically prepared films obtained Irom a-silylated monomers (a) pTh-E2, (b) pTh-E3, (c) pTh-El, A = 5145 A (Reprinted with permission from ref 10).

Table 14.11. / and p values (%) for polythiophene films electrochemically prepared from silylated monomers... 

Improvement of the structural order and conjugation in polythiophenes prepared from OL-silylated monomers... 

From both Raman and photoluminescence criteria the polymers prepared from a-silylated monomers appear as structurally more ordered and more conjugated than the polymers synthesized from related a-hydrogenated monomers. 

Synthesis of poly(3-alkylthiophene) from silylated monomers Poly(3-alkylthiophene) which are easily prepared by oxidative polymerization of 3-alkylthio-phene have also been synthesized upon oxydation of silylated 3-alkylthiophene (Scheme 14.39 and Table 14.14) [13]. The polymers are denoted pATh-n (n is defined in Table 14.14)... 

In order to characterize poly(3-alkylthiophene) prepared from silylated monomers, room-temperature photoluminescence experiments have been performed on polymers in solution (THF) [132]. Four samples have been studied poly(3-alkylthiophene) synthesized from hydrogenated and silylated monomer, respectively (the polymers are called pATh-1, 1 Table 14.14) and poly(3-alkylthiophene) synthesized from die two isomeric mono silylated monomer pATh-3,4 (Table 14.14). 

The same analysis has been made on polymers pA3Th-Cl and pA3Th-Cl (Table 14.16) prepared by chemical oxidative coupling using FeCl3 of a-hydro-genated and a-silylated monomers, respectively. The low-temperature photoluminescences taken on these two polymers are shown in Figure 14.40. 

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