Thermal stability of silicon-containing amide benzimidazole,hydrazide, and oxadiazole polymers

Studies were undertaken to ascertain the thermal stability of several types of silicon-containing polymers. Results of thermal analysis investigations indicate that all of the polymers are unusually heat-resistant when heated in air at elevated temperatures. Solution-cast films of the polymers on aluminum showed excellent flexibility and adhesion characteristics after being heated in air for 100 hr. at 300°C. and then for 3.5 hr. at 400°C. Visual examination of the films after the heating sequence indicated that the silicon-containing polyamides and polybenzimidazole had darkened slightly, while the polyoxadiazole appeared to be unaffected in this respect. Infrared spectroscopy studies showed that all of the polymers underwent only very minor structural changes during the prolonged heating process.     

The use of platinum and rhodium catalysts for the preparation and cationic ring-opening polymerization of silicon-containing epoxides

Regioselective platinum and rhodium catalysts were employed for the preparation of novel silicon-containing polyethers. First, silicon-containing monomers bearing cycloaliphatic epoxy groups were prepared by a rhodium-catalyzed regioselective hydrosilation. Then these monomers were polymerized using a platinum-catalyzed, cationic, ring-opening polymerization to give the linear polyethers. The obtained polyethers were compared with polymers prepared by photoinitiated cationic ring-opening polymerization using onium salt photoinitiators and found to be identical. © 1993 John Wiley & Sons, Inc.     

Silicon-containing polyoxadiazoles-synthesis and perspectives

A review is presented on those polymers which contain diphenylsilylene units and 1,3,4-oxadiazole rings either in the main chain or in the pendent groups. The synthesis of silicon-containing monomers as well as of the polyoxadiazoles based on them is described. The properties of these polymers, such as solubility, film forming ability, thermal stability, electrochemical behavior and photoluminescence properties, and their potential applications are discussed.     

Preparation of silicon-containing polymers IV. Thermally stable organosilicon poly-1,2,4-triazoles

Novel silicon-containing poly-1,2,4-triazoles have been synthesized by the reaction of polyhydrazide precursors and aniline in polyphosphoric acid (PPA) at 260°C. The polyhydrazide intermediates were prepared from aromatic dihydrazides and silicon-containing acid dichlorides via interfacial polycondensation. These polymers and their intermediates were characterized by infrared spectroscopy (IR), solubility, and by solution viscosity. The thermal behavior of these polytriazoles has been studied by dynamic thermogravimetry.     

Synthesis of new photosensitive silicon-containing poly(salicylideneazomethynes)

Photosensitive silicon-containing poly(salicylideneazomethynes) have been synthesized. It has been shown that these polymers are characterized by the presence of intramolecular donor-acceptor interactions between valence shells of silicon and nitrogen atoms; as a result, polyconjugation appears according to the nonclassical mechanism. The photo-and electrophysical properties of the polymers have been examined. The introduction of an oxygen spacer into a polymer facilitates an increase in the photosensitivity and quantum yield of free charge carrier photogeneration, and it has almost no effect on the conductive behavior of the polymers.     

Cone calorimetry studies of benzoxazine-epoxy systems flame retarded by chemically bonded phosphorus or silicon

The combustion behaviour of phosphorus- and silicon-containing benzoxazine-epoxy systems has been studied by LOI and cone calorimetry giving clear evidence that incorporation of 3.5% P into the benzoxazine-epoxy systems resulted in flame retardation while the silicon-containing copolymer was found to have no improvement in the LOI and cone calorimeter data, with values similar to the polymers without heteroatom, thus indicating that the 3.9% silicon content has no flame retarding effect. The peak heat release rate is reduced significantly for the phosphorus-containing benzoxazine as a result of a combination of condensed-phase and gas-phase mechanisms. The incorporation of phosphorus or silicon into the modified benzoxazine-epoxy system increases the smoke hazard and the CO emissions compared to the heteroatom-free system.     

Microporous structure of highly permeable additive silicon-containing polytricyclononenes

The porosity of a number of additive silicon-containing polytricyclononenes from the class of highly permeable polymers has been systematically studied for the first time by the method of low-temperature nitrogen adsorption/desorption. It has been shown that these polymers have a large specific surface area (390?790 m²/g) and are microporous. Dominant pore size ranges from 7 to 10 Å depending on the number of Me₃Si groups in a monomer unit and their relative position.     

SILICON-CONTAINING POLY(p-ARYLENE VINYLENE)S:SYNTHESIS AND PHOTOPHYSICS

A series of new silicon-containing poly(p-arylene vinylene)s(PAVs)with anthracene units in the main chain were synthesized by hydrosilylation reaction.The introduction of organosilicon units improved the solubility of the polymers,and theπ-πconjugation of polymeric chains was interrupted.These polymers behaved as blue-green light emitters with their fluorescence maximum at 447—499 nm and quantum yields in the range of 0.28-0.30 in solution.     

Silicon-Containing Condensation Polymers Derived from Long-Chain Fatty Acids

Silicon-containing condensation polymers were prepared starting from difunctional silicon-containing carboxylic acids or diols derived from long-chain fatty acids. Polyesters were synthesized by reaction of diacids containing siloxane linkages with diols, and diols containing siloxane linkages with various diacids. 1,3-Bis (10-carboxydecyl)tetramethyldisiloxane was condensed with various diamines to yield polyamides. 1,3-Bis(11-hydroxyundecyl)tetramethyldisiloxane and 1,3-bis [9(10)-hydroxyoctadecyl]tetramethyldisiloxane were condensed with diisocyanates to yield polyurethanes. Polycarbonates were synthesized by reacting the diols containing siloxane linkages with ethyl chloroformate. Some polybenzimidazols were synthesized by heating the diesters of the silicon-containing carboxylic acids with 3,3′ -diaminobenzidine. Some of the polyurethanes and polybenzimidazoles were thermally stable up to 300°C as indicated by TGA.     

POLYMERIZATION OF 1-BUTYL-2-TRIMETHYLSILYLACETYLENE BY TRANSITION METAL CATALYSTS

New silicon-containing disubstituted polyacetylene was prepared by the polymerization of BTMSA having two bulky substituents (n-butyl and trimethylsilyl) using transition metal catalysts. The polymerization proceeded in a mild manner and the final polymer yield was generally lower than those of silicon-containing monosubstituted acetylenes by the similar catalyst system. The characterization on the polymer structure revealed that the resulting poly(BTMSA) have a conjugated backbone system, but the polymers have peculiar copolymer composition of poly-(BTMSA) and poly(1-hexyne) due to the spontaneous desilylation during the polymerization. The fluoride-ion induced desilylation of poly(BTMSA) using n-Bu₄N⁺F^? in THF yielded a completely desilylated product, pure poly(1-hexyne).     

主链含硅的芳族聚酰胺的合成及其气体选择透过性能

采用界面缩合聚合方法，合成了一系列主链含硅的芳族聚酰胺，从化学结构与气体透过性能关系的角度研究了此类聚合物均质膜的气体透过性能，结果表明，此类聚合物膜对Ｈ２、Ｏ２、Ｎ２、ＣＯ２、ＣＨ４的气体透过系数大小顺序符合一般玻璃态聚合物规律；在刚性强的高分子链段中引进柔性基因，可提高聚合物的气体透过系数；高分子主链有较强内旋转能力的聚合物，气体透过系数大；高分子主链的化学结构相同，苯环上带有侧甲基的聚合物有高的气体透过系数；硅原子上带有侧苯基的聚合物，其气体扩散系数大于而溶解系数小于硅原子上携有侧甲基的聚合物．结论为，在刚性高分子主链中引入柔性基团和提高刚性链间隙是增大气体透过含硅聚酰胺膜速率的有利因素．     

New ferrocene-containing structures: Poly(silyl ester)s

Two new polymeric structures containing ferrocene units along the chains, namely poly(silyl ester)s, have been synthesized and characterized: a geminal poly(silyl ester) (g-PSE) and one having a disiloxane spacer between the silyl ester groups (s-PSE). The condensation polymerization of AA/BB monomer systems in solution was used in both cases as preparation method involving a silicon-containing diol, (diphenylsilane diol or 1,3-bis(hydroxy)-tetramethyldisiloxane), and 1,1′-di(chlorocarbonyl)ferrocene. The polymers were investigated by differential pulse voltammetry in order to evaluate the redox behavior. Due to the presence of the silyl ester groups in the chain, these polymers are hydrolytically degradable.     

Poly(amidoamine-organosilicon) (PAMAMOS) multi-arm star polymers

A new class of hydrophilic core – hydrophobic arms multi-arm star polymers is described: the first such materials to have silicon located in the side arms. They belong to the broad family of radially layered copolymeric amidoamine-organosilicon (PAMAMOS) dendritic macromolecules and may be viewed as nanostructured, covalently bonded, inverse micelles. Two types of hydrophobic, silicon-containing arms have been used, one based on polydimethylsiloxane (PDMS) and another based on predominantly alkyl chains attached by organosilicon chemistry to the hydrophilic polyamidoamine (PAMAM) core. The former polymers are synthesized by a reaction of amine-terminated PAMAMs by mono-functional epoxy PDMS, while the latter are obtained by haloalkylation of the same PAMAMs with a suitable unsaturated silane followed by alkylthiol addition. The Langmuir film behavior of the multi-arm star polymers with PDMS arms is described and rationalized in comparison with that of other hydrophobically modified PAMAM dendrimers reported in the literature. Their uptake of Cu²⁺ from aqueous solutions is also described.     

Living cationic polymerization of vinyl ethers with a functional group. VII. Polymerization of vinyl ethers with a silyloxyl group and synthesis of polyalcohols and related functional polymers

Living cationic polymerizations of two silicon-containing vinyl ethers, 2-(t-butyldimethyl-silyloxyl)ethyl vinyl ether (tBuSiVE) and 2-(trimethylsilyloxyl)ethyl vinyl ether (MeSiVE), have been achieved with use of the hydrogen iodide/iodine (HI/I₂) initiating system in toluene at ?15 or ?40°C, despite the existence of the acid-sensitive silyloxyl pendants. The living nature of the polymerizations was demonstrated by linear increases in the number-average molecular weights (M?_n) of the polymers in direct proportion to monomer conversion and by their further rise upon addition of a second monomer feed to a completely polymerized reaction mixture. The polymers obtained in these experiments all exhibited very narrow molecular weight distributions (MWD) with M?_w/M?_n around or below 1.1. Desilylation of the polymers under mild conditions (with H⁺ for MeSiVE and F^? for tBuSiVE) gave poly(2-hydroxyethyl vinyl ether), a water-soluble polyalcohol with a narrow MWD. The living processes also permitted clean syntheses of amphiphilic AB block copolymers and water-soluble methacrylate-type macromonomers, all of which bear narrowly distributed segments of the polyalcohol derived from the silicon-containing vinyl ethers.     

Plasma-substrate interaction: Effect of volatile oligomers in silicone rubber on plasma polymerization of fluorine-containing monomers

The cause of the conspicous Si content consistently observed on plasma polymers deposited on silicone rubber was investigated in this study. Plasma polymers of tetrafluoroethylene and of hexafluoroethane were deposited on the inside surface of Silastic tubings with and without oligomers by using a semicontinuous plasma polymerization reactor. This tube coating reactor is unique in the sense that the only surface which interacts with the plasma is the substrate surface (i.e., inside wall of tubing) and that plasma polymerization occurs in a very small volume of 3.3-mm-I.D. and 2-cm-long section of tubing at any given time. These two factors render the reactor a suitable system for the investigation of plasma-substrate surface interaction. Silastic tubings free of oligomers were prepared by extracting the tubings as received with distilled n-hexane for 3 h which yielded a 3% weight loss. It was found that the conspicuous Si content noted previously was not occasioned by the migration of oligomers through the plasma polymers but was caused by the redeposition of plasma copolymers formed from a mixture of the feed-in monomer and the silicon-containing volatile components evolved from the silicone rubber when exposed to the plasma. The presence of Si-containing compounds in the plasma evidently interfered with the plasma polymerization of tetrafluoroethylene and hexafluoroethane. Without volatile oligomers (the extracted samples), ESCA analysis indicated that the plasma polymers contained large amounts of CF₃, CF₂, and CF moieties, just like most typical plasma polymers of these monomers deposited on nonreactive substrates. With the presence of volatile oligomers, the fluorine content decreased drastically and a significant increase of oxygen-containing and silicon-containing moieties was observed. The influence of the volatile oligomers in the substrate on the balance between ablation and polymerization in plasma polymerization and its energy input level dependence (manifested by W/FM) were studied as well. The results were also discussed in relation to the bicyclic rapid step-growth polymerization mechanism.     

含硅金属化合物的研究进展

近年来,含硅金属化合物由于在催化工业等领域的广泛应用受到了化学工作者的重视。本文综述了以硅原子或硅杂链为配体的桥形成的金属络合物、金属硅氧烷、硅-金属化合物、金属不饱和硅化物、含硅多金属络合物五种含硅金属化合物的研究进展。最后,并对该领域的研究方向提出了展望。     

Permeation and sorption in polynorbornenes with organosilicon substituents

Gas sorption properties, permeability coefficients, and diffusion coefficients of a series of norbornene polymers are presented. Introduction of the Si(CH₃)₃ group into the polynorbornene (PNB) backbone chain results in significant increases in glass transition temperature, permeability, and diffusion coefficient for a number of gases (H₂, O₂, N₂, CO₂, CH₄, C₂H₆). The transport properties and sorption isotherms for poly(5-trimethylsilyl norbornene) (PTMSNB) are very similar to those for poly(vinyltrimethyl silane) (PVTMS), which contains the same side-chain group but differs from PTMSNB by the structure of its main chain. For another silicon-containing polymer poly[5-(1,1,3,3-tetramethyl-1,3-disilabutyl) norbornene] (PDSNB) having a bulkier side-chain group, the glass-transition temperature is decreased in comparison with that of PNB, presumably owing to self-plasticization. Both silicon-containing norbornene polymers (PTMSNB and PDSNB) have permeability coefficients for “rapid” gases like H₂ or CO₂ of about 10² Barrer. The high values of the Langmuir sorption capacity C′_H for PTMSNB and PVTMS, as well as the high diffusivity and mobility of spin probes in these polymers, were attributed to a large free volume related to the bulky Si(CH₃)₃ groups attached directly to the main chain. © 1993 John Wiley & Sons, Inc.     

Thermal stability and thermodynamic properties of hybrid proton-conducting polyaryl etherketones

The thermal and structural stability of sulfonated cross-linked PEEK (polyether ether ketone) and its silicon-containing class II hybrid derivatives were characterized by combination of mass spectrometry, infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry. Thermodynamic properties of the hybrids were determined, including glass-transition temperature, degree of crystallinity, and thermal stability. The decomposition processes of the hybrid polymers could be consistently interpreted and their energetics quantitatively determined. The introduction of inorganic silanol moieties improves the thermal stability compared to sulfonated products.     

Silicon-containing flame retardant epoxy resins: Synthesis, characterization and properties

Epoxy resins with different silicon contents were prepared from silicon-containing epoxides or silicon-containing prepolymers by curing with 4,4′-diaminodiphenylmethane. The reactivity of the silicon-based compounds toward amine curing agents was higher than that of the conventional epoxy resins. The T_g of the resulting thermosets was moderate and decreased when the silicon content increased. The onset decomposition temperatures decreased and the char yields increased when the silicon content increased. Epoxy resins had a high LOI value, according to the efficiency of silicon in improving flame retardance.