1994 рік

The miscibility and complexation behaviour of two isomeric tertiary amide polymers, poly(N,Ndimethylacrylamide) (PDMA) and poly(2-ethyl-2-oxazoline) (PEOx), with poly(styrene-co-allyl alcohol) (SAA) containing 4.5 and 6.5 wt% of hydroxyl groups has been studied. PDMA and SAA form complexes from methyl ethyl ketone (MEK) solutions when the PDMA contents in the feed are not more than 50 and 75 wt% for SAA(4.5)/PDMA and SAA(6.5)/PDMA, respectively. However, they do not form complexes from tetrahydrofuran (THF) or N,N-dimethylformamide (DMF) solutions. On the other hand, PEOx does not form complexes with SAA from any of the three solvents used. We have previously reported that another isomeric tertiary amide polymer, poly(N-methyl-N-vinylacetamide)( PMVAc), can form interpolymer complexes with SAA from MEK solutions over the entire feed composition range and from THF solutions when the feed is rich in SAA. These observations show that the abilities of the three isomeric tertiary amide polymers to form complexes with SAA are in the order of PMVAc> PDMA > PEOx. FTi.r. spectroscopy studies demonstrate that intermolecular hydrogen bonding interactions contribute to the miscibility and complex formation in these blends

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On preparation of the doubly oriented iodine-nylon 6 complex through iodine doping, modified double orientation is observed by X-ray diffraction. In iodine doping, double orientation of the complex is occasionally modified in the central part of a long strip of the doubly oriented specimen. Hydrogen-bonded planes of nylon 6 chains are oriented perpendicular to both film surfaces of the specimen with modified orientation, while in normal doubly oriented specimens the planes are oriented parallel to the surfaces, as in the nylon 6 ~-form. Even in the modified specimens, the orientation of the chain axis is maintained parallel to the draw direction. Iodine doping gives rise to rotation of double orientation at an angle of 90 ° about the draw direction. The modification is thought to be due to diffusion of polyiodide ions through the film surfaces of the specimen

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The thermal behaviour of nylon 66, associated with the morphologies identified previously, has been examined. The thermograms for the crystallization temperatures (T~), between 247°C and 265°C, were distinctly different from those at low T? and from those given by samples crystallized non-isothermally on cooling. The endothermic peak could be identified with the melting of negative and zero birefringent spherulites (the latter of both kinds). On cooling, samples crystallized in the T? range of 247-265°C, display certain characteristic exotherms indicating further crystallization. In view of the fact that 'morphologically' the preceding crystallization had been complete, such crystallization must take place within the appropriate morphological entities themselves, conforming to the particular morphology present already, or alternatively the effect may correspond to a solid-solid transformation. In addition to the above, a new high melting crystal form with Tm in the range of 280-285°C has become apparent forming under conditions corresponding to zero birefringent spherulites (high To) but distinct from the latter, not conforming to any morphology seen in our previous study. Finally, the new information and issues arising therefrom are summarized and placed in perspective

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Mixtures of high-molecular-weight hydrogenous, syndiotactic poly(methyl methacrylate) with two lower-molecular-weight deutero poly(methyl methacrylate)s have been investigated over a range of temperatures and compositions using small-angle neutron scattering. Effective interaction parameters have been obtained which have been used to estimate the Flory-Huggins interaction parameter. Spinodal temperatures have been defined from the temperature dependence of these effective interaction parameters and other parameters of the mixtures. The conclusion is that these isotopic mixtures are incompatible at ambient temperatures and have an upper critical solution temperature. The influence of local stereochemistry on the polymer configuration is evident in the scattering cross-section variation with scattering vector. This variation is compared with the scattering obtained from Monte Carlo rotational isomeric state calculations.

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The gelation of several samples of atactic polystyrene (aPS) in CS2 is studied by rheological methods. The Young's modulus and the loss and storage moduli are measured as a function of temperature in the sol and gel phases. In the sol phase the concentration dependence of the plateau modulus, Gr~, is found to be in good agreement with the theoretical predictions. The sol-gel transition is accompanied by an abrupt increase of GN, which shows the formation of additional entanglements with respect to the sol. For temperatures, T, below the gelation temperature, Tg?l , G N does not vary with temperature and the gel seems to reach a final structure at T = Tgel- 10°C. These behaviours, which are independent of the aPS molecular weight, are discussed in relation to other experimental investigations (phase diagram, anisotropic light scattering, neutron scattering)

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The viscometric behaviour of high molecular mass polyamide 6, prepared by activated anionic polymerization of e-caprolactam in a twin-screw extruder, has been studied in 90% formic acid. Results obtained show that viscosity number increases with polymer concentrations to -,~ 0.001 or 0.0015 g ml-1, but unexpectedly declines thereafter. Whereas anomalous results are obtained at a concentration level of 0.005gml-~, as specified in ISO 307:1984, at very low solution concentration, viscometry data correlate well with findings from g.p.c.

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Micelle formation and decomposition were investigated by static and dynamic light scattering for the diblock copolymer poly(ct-methylstyrene)-block-poly(vinyl-p-phenethyl alcohol) (P~tMS-b-PVPA) with asymmetric block composition [PctMS]/[PVPA] = 90/10 (in molar mass) in mixed solvents, one component solvent, m-chlorobenzyl chloride (CBC), being selective for the PctMS block and the other, m-chlorobenzyl alcohol (CBA), being so for the PVPA block. Core-corona type micelles were formed in both pure solvents: micelles in CBA were dense star-shaped 'crew-cut' ones having a large swollen core with a thin corona layer, and those in CBC were star-shaped ones having a small core with long corona chains. Micelle decomposition was observed in both CBA- and CBC-rich solvents within a narrow range of solvent composition as the other component solvent was being added to a pure solvent. In the case of micelles formed in CBA-rich solvents, micellization could be induced by decreasing the temperature, while the micelles in CBC-rich solvents could not be decomposed in the ordinary temperature range. The temperature-induced micellization transition at higher polymer concentrations took place with no appreciable increase of micelle fraction but primarily with an increase of association number. On the other hand, in the transition region at a lower concentration, change of micelle fraction dominated over variation of association number. From these results, the following were suggested: the critical micelle concentration cmc* near the critical micelle temperature was located at a relatively high concentration in CBA-rich solvents, while the micelles formed in CBC-rich solvents were more stable having lower cmc*.

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Polyurethane-ureas with dibenzo-18-crown-6 in the rigid chain fragments were characterized by small-angle X-ray scattering (SAXS), differential scanning calorimetry (d.s.c.), deformation calorimetry and gas transport measurements. As-cast samples are structurally microheterogeneous systems in which the composition and the relative content of different microphases varies with the chain length and the chemical nature of the soft component. As a general trend, the thermodynamic affinity between rigid and soft fragments becomes worse (i.e. the degree of microphase separation ~* increases) when the chain length of the latter increases and/or when an oligoether component is replaced with an oligoester of similar length. Thermoelastic and gas transport properties of the samples depend not only on their nominal chemical composition and ~* but also on the pattern of molecular packing within the rigid fragment-containing microphases.

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Linear low-density polyethylene (LLDPE) was irradiated with electron beam radiation at room temperature and in the melt. It was found that the gel point, as measured by an insoluble fraction in boiling xylene, occurred at a slightly lower radiation dose for melt irradiated samples. The melt radiation-crosslinked samples showed different melt rheological properties from the room-temperature radiation-crosslinked samples, as exemplified by the stress relaxing more slowly in a step strain experiment (relaxation modulus) for the former at a given radiation dose. The relaxation modulus could be fitted to a power-law expression consisting of two parameters, which, when plotted against each other, resulted in a single master curve for both irradiation temperatures. The curve showed two distinct regions of differing slope, which intersect at a point argued to represent a pseudogel point.

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An electrochemical method has been developed that enables production of conductive electroactive polymer colloids. This method involves the use of a flow-through electrochemical cell with a porous electrode. Polymerization is carried out in the presence of steric stabilizers. Colloids containing a range of different counterions can be produced

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