Synthesis and characterization of phenylquinoxaline-arylene ester block copolymers

Summary Phenylquinoxaline-arylene ester block copolymers were prepared from phenolic hydroxyl terminated oligomers of defined molecular weight using an oligomer/monomer(s) approach, in which generation of the ester linkage coupling the blocks occurred concomitantly with the growth of the polyester block. The molecular weight of the phenylquinoxaline block was held constant at 12,900, while the stoichiometry of the arylene ester monomers were adjusted to afford copolymers containing 15, 30, and 50 wt% poly(arylene ester). These copolymers represent the first example of PPQ-based block copolymers derived from well defined phenylquinoxaline oligomers.     

Lyotropic liquid crystalline phase of polyesteramides with different ratio of amide to ester groups in a main chain

Summary Various lyotropic liquid crystalline polyesteramides were prepared from 1,3-bis(4-aminobenzoyloxy)benzene, p-phenylene diamine, and terephthalic acid by changing the ratio of amide to ester groups and were observed by using a cross polarized light microscope. The range of liquid crystalline phase becomes wider with increasing the portion of amide groups in a main chain because the chain rigidity becomes higher and the polymer-solvent interaction stronger. In the case of polyesteramides with flexible spacers, the polymer with one p-phenylene group between two ester groups does not form an anisotropic phase but the polymer with the same group between amide groups shows an anisotropy.     

Structure of AB block copolymers with a polypeptide block: Effect of the chain conformation

The structure of AB copolymers with a polypeptide block has been studied by X-ray diffraction, electron microscopy, infrared spectroscopy, and circular dichroism. Copolymers with a polyvinyl block (polybutadiene or polystyrene) and a hydrophobic polypeptide block (polybenzyl-L-glutamate or polycarbobenzoxy-L-lysine) exhibit a lamellar structure in the dry state and in solution in dioxane or in different chlorinated solvents. This lamellar structure consists of plane, parallel, equidistant sheets. Each sheet results from the superposition of two layers: one formed by the polyvinyl chains in amore or less random coil conformation, the other formed by the polypeptide chains in an α-helix conformation, arranged in a hexagonal array and generally folded. Copolymers with a polyvinyl block and a hydrophilic polypeptide block (poly-Llysine or poly-L-glutamic acid) exhibit a larnellar structure in water solution and in the dry state. The difference between this lamellar structure and the preceding one consists in the conformation of the polypeptide chains: an intramolecular mixture of coiled chains, α-helices, and β chains. Copolymers with a polysaccharide block and a hydrophobic polypeptide block exhibit in DMSO solution and in the dry state a lamellar structure similar to that of copolymers with a polyvinyl block and a hydrophobic polypeptide block.     

Accelerated pressure synthesis and characterization of 2-oxazoline block copolymers

The cationic ring-opening polymerization of 2-oxazolines in acetonitrile was investigated under pressure conditions utilizing methyl tosylate as initiator of which the single crystal X-ray structure is described as well. The polymerization kinetics were studied and compared with previously reported microwave-assisted pressure polymerizations. Moreover, a series of block copolymers was synthesized in an automated parallel synthesis robot utilizing this pressure polymerization method. The resulting block copolymers were characterized with both differential scanning calorimetry and contact angle measurements to determine the effect of copolymer composition on glass transition temperature, melting point and surface energy. Atomic force microscopy was applied to further investigate the possible phase separation.     

Polymers with mesogenic elements in the main chain: A nematic aromatic copolyester

Properties of a copolyester based on methylhydroquinone, pyrocatechol and terephthalic acid have been described. Light scattering data for the copolyester in chloroform and dichloroacetic acid are well represented by $\text{M}\text{?}{}_{\mathrm{w}}\text{=220 000}$ while the intrinsic viscosity is 0.22 dl g^?1, which implies a compact arrangement of the molecule in dilute solution. Differential scanning calorimetry (d.s.c.) traces show that the copolyester is essentially non-crystalline in character. Polarizing microscopy (texture observations, miscibility tests) provides definite proof as to the nematic structure of the melt. Well aligned samples can be produced either by subjecting nematic melt to a magnetic field (H_c = 0.6 T) or by suitable treatments of the slides between which the melt is observed. The conoscopic interference pattern corresponds to that of a uniaxial system showing an optically positive character. A structural model is proposed to account for the X-ray patterns obtained from oriented samples.     

Critical stress cracking of polymers with phenylene groups in the main chain

Polymers with phenylene groups in the main chain have been examined under uniaxial tension for their reactions to liquids. Preliminary results and critical values of the stress for breaking on liquid contact at room temperature are given.     

丙烯与极性单体嵌段共聚合的研究进展

综述了近年来聚丙烯基嵌段共聚物合成方法的研究进展。通过选用合适的Ti催化剂能够直接催化丙烯与降冰片烯和/或甲基丙烯酸甲酯进行聚合,从而通过活性聚合的方式直接得到聚丙烯基嵌段共聚物。合适的聚合条件下,链转移剂的加入能够在聚合过程中产生金属―C键,再经氧化酸化后得到末端羟基,实现聚丙烯的端基功能化。将端基功能化与可控自由基反应、点击反应、偶联反应相结合能够得到聚丙烯基嵌段共聚物。通过催化剂的结构优化设计,配合合适的链转移剂,能够调控聚丙烯基嵌段共聚物的结构。     

Heterocyclic polyimides containing siloxane groups in the main chain

BACKGROUND: Among the polymers widely studied for applications in advanced techniques, aromatic polyimides have received considerable attention due to their outstanding thermal stability associated with good electrical and mechanical properties. However, these polymers are usually difficult to process, being insoluble and without a glass transition. To improve the processing characteristics of polyimides, modification of their structure is often achieved by the introduction of flexible linkages in the macromolecular chain or various substituents on the aromatic rings. RESULTS: A series of polyimides and intermediate polyamidic acids were synthesized from aromatic oxadiazole‐diamines and a dianhydride containing a siloxane bridge (? R₂Si? O? SiR₂? ). These polymers exhibit good solubility in certain organic solvents and can be cast into thin and very thin films from their solutions. They exhibit high thermal stability with decomposition being above 440 °C and relatively low glass transition temperatures in the range 160–190 °C. These polymers show strong photoluminescence in the blue spectral region. CONCLUSION: The introduction of oxadiazole rings together with siloxane groups into the chains of aromatic polyimides gives highly thermostable polymers with remarkable solubility and film‐forming ability and that emit blue light, being attractive for applications in micro‐ and nanoelectronics and other related advanced fields. Copyright © 2009 Society of Chemical Industry     

Porous bead polyaromatic copolymers containing ester groups. II. The influence of the preparation conditions on surface properties of copolymers

Porous bead copolymers of styrene with 4,4′-di(methacryloyloxymethyl)diphenylmethane (DMD) have been prepared. Preparation conditions (composition of the monomer mixture with an inert component) were discussed with respect to the porous properties of copolymers (the specific surface area, pore size distribution and mean pore radius).     

Polymers with mesogenic elements and flexible spacers in the main chain: Aromatic-aliphatic polyesters

A new series of aromatic-aliphatic polyesters of general structure: R₁ = terphenyl, biphenyl, stilbene R₂ = (CH₂)_n; ? CH₂? C(Me)₂? CH₂? ;? CH₂;? C(Et)₂? CH₂? ; (CH₂? CH₂? O)_n CH₂? CH₂? has been synthesised. The existence of thermotrpic liquid crystalline phases has been shown by polarised light microscopy. The texture observations have suggested the existence of nematic, S_A or/and S_C phases depending on the chemical structure. The temperature of transition between the phases and, as a consequence, the range of mesomorphism are highly dependent upon the chemical structure. The clearing point is high, even for the longest aliphatic group, while the melting point is depressed.     

Controlled synthesis of amphiphilic siloxane-siloxane block copolymers with carboxyl functions

Summary Poly[2-(carboxymethylthio)ethyl]methylsiloxane-block-polydimethylsiloxane, 1, and poly{[2-(carboxymethylthio)ethyl]methylsiloxane-co-dimethylsiloxane}-block-polydimethylsiloxane, 2, were synthesized by ene-thiol addition of mercaptoacetic acid to respective precopolymers 3 and 4, containing vinyl groups bound to silicon. The precopolymers 3 and 4 were obtained by sequential anionic copolymerization of hexamethylcyclotrisiloxane, D₃, with 2,4,6-trimethyl-2,4,6-trivinyl-cyclotrisiloxane, 5, and D₃ with 2,4,4,6,6,-pentamethyl-2-vinylcyclotrisiloxane, 6, respectively. The method permits to synthesise the block copolymers with a narrow molecular weight distribution and a high block purity. The ene-thiol addition was performed on free radical route, using AIBN as initiator. The reaction proceeds selectively, leading to the transformation of vinyl groups in the precopolymers into the β-adducts. Received: 15 December 1999/Revised version: 25 February 2000/Accepted: 24 March 2000     

Porous bead polyaromatic copolymers containing ester groups. IV. Testing for gelpermeation chromatography

In this paper a new type of porous polymeric sorbents of 4,4′-di(methacryloyloxymethyl)diphenyl ether (DME) and styrene as a GPC column packing material has been investigated. The tested DME-styrene copolymers had molecular sieve properties and separation and elution was in accordance with the exclusion mechanism. The applied preparative procedure gives packings which do not vary considerably in their porosity.     

新型聚硅氧烷嵌段共聚物的合成研究进展

聚硅氧烷作为一种有机硅高聚物,可通过嵌段共聚进行相应的化学改性。综述了国内外新型聚硅氧烷嵌段共聚物的研究进展,主要对纯聚硅氧烷嵌段型、聚醚型、聚烯烃型和聚氨酯型进行了叙述,并对其应用前景进行了展望。     

Thermally curable polyurethanes containing naphthoxazine groups in the main chain

A new methodology has been developed for the modification of polyurethanes with reactive naphthoxazine moieties in order to expand their industrial applicability as electrical insulators. Thermoplastic and organosoluble poly(urethane‐co‐naphthoxazine)s were prepared by the reaction of NCO‐terminated urethane prepolymers made from various soft segments with a naphthoxazine‐containing diol chain extender. The prepared polymers were easily processed into thin films using either solution casting or compression moulding techniques. Heat treatment of these films under optimized conditions (200 °C for 30 min) led to the thermally activated ring‐opening polymerization of naphthoxazine moieties, and consequently crosslinked networks were obtained. All of the starting materials and the final polymeric compounds were fully characterized using spectroscopic methods and their physical and chemical properties evaluated and then correlated with their chemical structures. Due to their good elongation property (up to 70% elongation at break) in comparison to polynaphthoxazines, significant enhancement in decomposition temperature as well as high value of dielectric breakdown strength (up to 30 kV mm^?1) in comparison to polyurethanes, these materials are potentially applicable as electrical insulators with service temperatures higher than those for related unmodified polyurethanes. Copyright © 2010 Society of Chemical Industry     

Amphiphilic block copolymers with pendant thiol groups in side chains by RAFT polymerization

A new synthetic approach to thiol functional, well-defined amphiphilic block copolymers, which can be used to prepare multifunctional polymers and polymeric nanoparticles, is presented. Starting with a hydrophilic macroRAFT transfer agent and hydrophobic (meth)acrylate monomers that possess protected thiol groups, amphiphilic block copolymers are prepared in high yield. It is proven that the protected thiol groups in the monomer do not interfere with the RAFT polymerization process. Polymers with defined molecular weight, narrow polydispersities (PDI < 1.30) and varying length of the hydrophobic block are presented. Polymers with thiol groups in side chains and chain ends are obtained by aminolysis. With pyrene fluorescence spectroscopy and NMR measurements, it is shown that all synthesized polymers self-assemble into micelles. Furthermore, the possible application of these new polymers is exemplified by the preparation of polymer nanoparticles.     

Properties of side chain liquid crystal polyesters containing chiral groups in the main chain

The synthesis and investigation are reported for the phase behavior of a set of three liquid-crystalline side chain polyesters (SCLCPs), consisting of aromatic diacids and diols bearing cyano biphenyl moieties in the side chain. The materials contain a chiral center in the main chain and show a cholesteric phase indicative of a helical order with a preferred twist. In addition, they exhibit T_g's below room temperature and smectic bilayer phases. Depending on the substitution pattern of the aromatic core, S_c* or S_A* phases are observed. These polymers were synthesized in a four-step synthesis, starting from available materials. The dielectric relaxation behavior and the pyroelectric responses of the three SCLCPs tend to conform to their respective structure.     

Cationic polyelectrolytes,XI. Polymers with quaternary N-atoms in the main chain obtained by condensation polymerization of epichlorohydrin with amines

Water soluble cationic polyelectrolytes containing quaternary nitrogen atoms within the main chain were prepared via condensation polymerization of epichlorohydrin (ECH) with dimethylamine (DMA) and N,N-dialkylaminoalkylamines. The main parameters of the reaction that influence the polymer properties are: DMA/asymmetrical diamine molar ratio, the initial concentration of amine solution, NaOH/amine molar ratio, ECH/amine molar ratio, and asymmetrical diamine structure. The feature of flexible polyelectrolyte own to the investigated polymers was emphasized by the viscosimetric behaviour in dilute aqueous solutions with and without salt presence.     

Synthesis and photochemical crosslinking of block copolymers: styrene-isoprene grafted with photosensitive groups

Summary This paper is relative to the synthesis and the photocrosslinking of a copolymer (styrene/isoprene) which is grafted with cinnamic structures, to give high added value to hydrocarbon polymers. The films of copolymers are irradiated in the presence of photosensibilizers and the decrease of double bonds are analysed by UV spectroscopy.     

Towards the synthesis of electroactive block copolymers via anionic-to-Ziegler-Natta transformation reactions

Summary Diblock copolymers of acetylene and styrene were prepared by treating Ti(OBu)₄ with polystyryl lithium followed by reaction with acetylene. Reliable evidence for the formation of block copolymers was derived from dual radiotagging experiments.     

Random copolymers of propylene with 1,5-hexadiene containing only cyclopentane units in main chain and tailoring structure and mechanical properties of the copolymers

In the presence of [Ph₃C][B(C₆F₅)₄] and Triisobutylaluminium, dimethyl pyridylamidohafnium complex exhibited remarkable catalytic activity in the copolymerization of propylene with 1,5-hexadiene, affording high molecular weight copolymers with unimodal molecular weight distributions. More noticeably, the resultant copolymers contain absolutely cyclo-group in the polymer chains without pendent vinyl groups and crosslinking. The solid state structures and properties of the homogeneous copolymers were studied by examining melting behavior, wide-angle X-ray scattering, and tensile deformation. Chain microstructures were analyzed by ¹³C NMR spectra, and further confirmed by the measurement of reactivity ratios of the two monomers. These copolymers display a random distribution of the comonomer, and crystallinity decreases with increasing comonomer content. The copolymers contain variable amounts of comonomeric units, showing desired physical properties ranging from thermoplastic to elastoplastomeric to elastomeric.