Series Of Side-chain Polymers Research Articles

Effect of the degree of substitution in the transition temperatures and hydrophobicity of hydroxypropyl cellulose esters

We have synthesized and characterized five members of a homologous series of side chain polymers of hydroxypropyl cellulose esters obtained by homogeneous esterification with 6-[4′-(ethoxycarbonyl)biphenyl-4-yloxy]hexanoic acid. Two acylation procedures were studied. One procedure involved the acid chloride derivative and the other one was the activation of that acid with N,N′-carbonyldiimidazol. The second method yielded esters with higher degree of substitution, DS¯. The esters, with DS¯ ranging from 26 to about 66%, were characterized by FTIR, NMR, solution viscometry, TGA, DSC, polarized optical microscopy, and X-ray diffraction, in order to study the effect of the degree of substitution on the hydrophobicity, on the transition temperatures and on their potential liquid crystal properties. It has been found that the hydrophobicity and the transition temperatures of the HPC derivatives are very much dependent on the degree of acylation. The esters with high DS¯ values showed liquid crystal properties.

Synthesis and Mesophase Properties of a Series of Chiral Rod-Like Polysiloxanes

Cholesteric liquid crystals elastomers have been extensively studied during the last two decades. They showed Bragg-reflection in visible, Infrared and even UV wavelength Range and a particular circular polarization. Their special helical structure and the adjustment of pitch made them suitable for using as optical thin films. In this study, two kinds of mesogenic monomers undecylenate cholesteryl ester (M1) and p-phenylene di-4-(allyloxyl) benzoate (M2) were synthesized. Then the two monomers were fixed onto poly- (methylsiloxane) backbone by grafting polymerization using Dicyclopentadienylplatinum (II) Chloride as catalyst. A series of side-chain polymers with different monomer densities produced by the reaction of hydropolysiloxane and M1/M2with different molar ratios were obtained. The synthesized polymers were characterized by IR, H1NMR and GPC. The mesophases were characterized by using differential scanning calorimetry (DSC), polarizing optical microscopy (POM).

ChemInform Abstract: Linear and Hyperbranched Polycarbosilanes with Si-CH2-Si Bridging Groups: A Synthetic Platform for the Construction of Novel Functional Polymeric Materials.

Work carried in the authors’ laboratory on Si‐ CH2‐Si bridged polycarbosilanes is reviewed. In pursuit of high-yield polymeric precursors to silicon carbide, convenient synthetic routes to both linear and hyperbranched polycarbosilanes having a ‘[SiH2CH2]n’ compositional formula have been developed. The linear [SiH2CH2]n polymer was prepared by ring-opening polymerization of a substituted disilacyclobutane, and was studied both as an analogue of polyethylene and as a high-yield precursor to SiC. Elaboration of the methods employed to prepare this polymer has yielded a wide range of new poly(silylenemethylene)s (PSMs) of the type [SiRR’CH2]n, where R and R’ can be a wide range of different groups, including a series of symmetrically disubstituted polymers with R=R ’= F, alkyl and alkoxy which form crystalline solid phases and various amorphous, atactic polymers having different R and R’ groups. By using (Si)‐Cl replacement reactions analogous to those developed previously for polydichlorophosphazene, as well as hydrosilation reactions similar to those used for [Si(H)(Me)O]n, a series of side-chain polymers having various groups attached to Si through Si‐C or Si‐O bonded linkages were obtained. Similar polymer modification reactions have recently been developed for the branched oligomer/polymer analogue of these linear polycarbosilanes, leading to hyperbranched species with functional substituents, including a di(ethyleneoxy) methyl ether-terminated derivative which readily dissolves lithium salts. The results of studies of these novel ‘inorganic/organic’ hybrid polycarbosilanes are described and their properties are compared with those of related carbon-backbone and siloxane polymers. # 1998 John Wiley & Sons, Ltd.

Linear and hyperbranched polycarbosilanes with Si-CH2-Si bridging groups: A synthetic platform for the construction of novel functional polymeric materials

Work carried in the authors’ laboratory on Si‐ CH2‐Si bridged polycarbosilanes is reviewed. In pursuit of high-yield polymeric precursors to silicon carbide, convenient synthetic routes to both linear and hyperbranched polycarbosilanes having a ‘[SiH2CH2]n’ compositional formula have been developed. The linear [SiH2CH2]n polymer was prepared by ring-opening polymerization of a substituted disilacyclobutane, and was studied both as an analogue of polyethylene and as a high-yield precursor to SiC. Elaboration of the methods employed to prepare this polymer has yielded a wide range of new poly(silylenemethylene)s (PSMs) of the type [SiRR’CH2]n, where R and R’ can be a wide range of different groups, including a series of symmetrically disubstituted polymers with R=R ’= F, alkyl and alkoxy which form crystalline solid phases and various amorphous, atactic polymers having different R and R’ groups. By using (Si)‐Cl replacement reactions analogous to those developed previously for polydichlorophosphazene, as well as hydrosilation reactions similar to those used for [Si(H)(Me)O]n, a series of side-chain polymers having various groups attached to Si through Si‐C or Si‐O bonded linkages were obtained. Similar polymer modification reactions have recently been developed for the branched oligomer/polymer analogue of these linear polycarbosilanes, leading to hyperbranched species with functional substituents, including a di(ethyleneoxy) methyl ether-terminated derivative which readily dissolves lithium salts. The results of studies of these novel ‘inorganic/organic’ hybrid polycarbosilanes are described and their properties are compared with those of related carbon-backbone and siloxane polymers. # 1998 John Wiley & Sons, Ltd.

Self‐compacting smectic polymers. An unusual temperature dependence of interlayer distance for side chain polysiloxanes in sm a and sm b phases

AbstractA prominent reduction of the layer thickness, d1, in the Sm A and Sm B phases with increasing temperature has been observed for a series of side chain polymers. The maximum decrease in d1 value for one of the copolymers is ∼7Å; i.e. 15% of its total value. The influence of the chemical structure of the main chain and side groups on the effect has been studied. Models have been proposed for packing of mesogenic side groups at different temperatures.