1993 рік

Vinylbenzyl-terminated poly(styrene-b-isoprene) AB type diblock macromonomers were prepared by the direct coupling of corresponding living diblock anions with a large excess of p-chloromethylstyrene. (AB). type star-block copolymers were synthesized by microgelation in micelles formed by diblock macromonomer with ethylene glycol dimethacrylate as a linking agent. We studied the self-micellization of (AB), type star-block copolymers as a parameter of arm number (n) from electron microscopy observations

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An attempt to synthesize a series of phenyl ring disubstituted poly(o-, m- and p-phenylene vinylene) is reported. In this 'one-pot' reaction, a phase-transfer catalyst was used to promote the extraction of strong base deprotonated bischloromethyl aromatic anions from the aqueous to the organic phase to sustain a nucleophilic substitution reaction with the remaining bischloromethyl monomers. The polymers obtained were characterized for their chemical compositions and physical properties by elemental, i.r. and u.v. spectroscopic, and thermal analyses. The o-substituted polymers were found to have low melting temperatures, good solubilities and high molecular weights, but low yields. The m-substituted monomers, however, produced only non-conjugated poly-m-xylylenes. The p-substituted polymers offered the best combination of yield and physical properties. Films cast from soluble poly(2,5-dibutoxy-p-phenylene vinylene) have electrical volume resistivity in the range 300-500 ohm cm when doped with concentrated sulfuric acid.

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This study completes the investigation of the phase behaviour of polymer blends involving styrene (S), ortho-ftuoro styrene IoFS) and para-fluoro styrene (pFS). As before, due to the proximity of the glass transition temperatures of most blends investigated, the miscibility or immiscibility is established using the alternative thermal analysis method based on enthalpy recovery of samples annealed in the glassy state. In most respects the phase behaviour is similar to that of the corresponding chlorinated systems. The value of the Flory-Huggins parameter ~s,ovs is much smaller than ZS,pFS. However, the latter is approximately the same as XoFS,pFS and, as a consequence, a miscibility window as found in the system PS/P (oC1S-co-pC1S) is only present in PS/P(oFS-co-pFS) blends for rather low molecular weights

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The phase behaviour of syndiotactic polystyrene-decalin is studied by differential scanning calorimetry, wide-angle X-ray scattering and thermogravimetric analysis. Both the trans and cis isomers of the solvent have been used. The polymer chain can adopt a helix or a zigzag conformation. The formation of these conformations and their relative contribution to the crystalline structure depend on the initial concentration, the scanning rate and the thermal history of the samples. High cooling rates and low polymer concentrations tend to favour the formation of the helix structure. The conformational transition from the helix to the zigzag conformation can take place on heating. This depends on the experimental conditions

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The radiation stability upon exposure to high-energy radiation of different bi- and terpolymers such as poly[propylene-co-4-(hept-6-enyl)-2,6-di-tert-butylphenol], poly(propylene-co-6-phenylhex-l-ene) and p••y[pr•py•ene-c•-4-(hept-6-eny•)-2•6-di-tert-buty•phen••-c•-4-(hex-5-eny•)-2•2•6•6-tetramethy•piperidine] was studied. The films were exposed to a radiation dose of 25 kGy. The extent of radiation-induced degradation of the samples was determined by size exclusion chromatography. The most stable polymers found were a copolymer containing 0.82 wt% of 4-(hept-6-enyl)-2,6-di-tert-butylphenol and a commercial radiationresistant polypropylene. The copolymers containing chemically bound hindered phenol moieties exhibited better protective properties than polypropylene reference samples containing the same concentration of admixed 3-(3,5-di-tert-butyl-4-hydroxylphenyl)propionate (Irganox 1010). The copolymers containing 6-phenylhex-1-ene or admixed phenyl decane showed reasonably good stability against radiation, whereas the formulations containing hindered amine light stabilizers showed relatively poor radiation stability.

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Uniform-size polystyrenes (PSs) having a diol end-group 2 were synthesized through the reaction of a living PS with a chlorosilane derivative having a trimethylsilyl-protected diol function, i.e. 3-chlorodimethylpropoxy-l,2-bis(trimethylsiloxy)propane 1, and the subsequent deprotection by precipitation into an acidic methanol solution. The polyaddition reaction of 2 with 4,4'- diphenylmethanediisocyanate followed by the chain extension with 1,4-butanediol produced polyurethane- PS graft copolymers 3 with a controlled graft segment length and graft content

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This paper describes a one-step, room temperature synthesis utilizing ultrasonic energy of a coaxially stacked poly(phthalocyanato) germanium oxide ([Ge(Pc)O].) from Ge(Pc)C12. The synthesis is conducted in the presence of a sodium chalcogenide. Based on photoacoustic FTi.r. and u.v.-vis. spectroscopic analysis, the mechanism of the [Ge(Pc)O], formation is proposed. The use of isotopic H20/D20 exchange is also utilized in an effort to reveal the role of traces of water present during the polymerization reaction

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Oxygen permeation through films of pure poly(propylene) (iPP) and iPP blended with a fully saturated alicyclic hydrocarbon resin (IST), obtained by oligomerization of indonaphthene, ct-methylstyrene and vinyltoluene, was studied as a function of temperature and weight fraction of the two components. Increasing IST content lowers oxygen permeability and increases the glass transition temperature of the polymer blends. Annealing for 2 min at 375 K was shown to transform completely the smectic phase in the ~t crystalline form, while annealing for 10 min at 393 or 403 K induces a marked increase in crystallinity and in effective oxygen permeability per unit of amorphous component, Pa. This experimental behaviour may be explained by the formation of microvoids; the increase in microporosity modifies the mechanism of the permeation process.

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A study has been made of the transverse stretching of poly(ethylene terephthalate) film previously drawn longitudinally at constant force and width. The crystalline phase has been characterized using wide-angle X-ray diffraction: the orientation of the chain axis and the normal to the phenylene ring have been determined, as well as the crystallite size. Infra-red spectroscopy and refractive index measurements have been used to characterize the orientation of the material averaged over the crystalline and amorphous phases. The results showed that the crystals, which were preferentially aligned with their chain axes along the first stretching (longitudinal) direction, break down during the second drawing and that recrystallization takes place to produce crystallites with their c-axes aligned along the transverse stretching direction. The observed increase in the tendency for the normal to the phenylene ring to be normal to the film plane correlates with the increase in crystallite size along the chain axis for crystallites oriented with their chain axes in the transverse direction.

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Copolymer segregation behaviour has been studied using the technique of neutron critical reflection from layered samples. Surface segregation occurs due to location at the air/polymer interface of a copolymer microphase-segregated layer. Similar microphase segregation by the copolymer occurs during mutual diffusion with the homopolymer. By comparison with theoretical predictions, this segregation is shown to exhibit behaviour characteristic of end-tethered polymer brushes.

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