1994 рік

Polymer microsphere composed of monodispersed poly(4-vinyl pyridine) core-polystyrene (PS) shell [poly(4-vinyl pyridine) 28 mol%; number-average molecular weight (~,) of shell chain, 8.0 x 104; arm number, 1400] was blended with poly(styrene-b-2-vinyl pyridine) diblock copolymer [poly(2-vinyl pyridine) 30 mol%; ~t of PS =2.0 x 104], poly(styrene-b-isoprene) diblock copolymer (polyisoprene 28 mol%; ~r of PS = 2.6 x 104) or poly(styrene-b-4-vinyl pyridine) diblock copolymer [poly(4-vinyl pyridine) 17 mol%; M, of PS = 3.9 x 105]. The morphology of the blend was investigated by transmission electron microscopy. When M. of the diblock copolymer was less than 3.2 x 104, a well-ordered arrangement of the microsphere and the spherical microdomains of block copolymer in the PS matrix was observed in two dimensions. The degree of order of the spherical microdomain was estimated using the radial distribution function

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The morphology of polymer blends of poly(e-caprolactone) (PCL) and poly(vinyl methyl ether) (PVME) is compared with that of PCL and a random copolymer of styrene and acrylonitrile (SAN). The main objective is to determine the influence of the glass transition temperature of the amorphous component (TB,,) on the morphology of the semicrystalline polymer blends. These blends represent the two extreme cases corresponding to Tc < Ts,a and Tc > Tg.,, where Tc is the crystallization temperature. The morphology of these blends, with PVME and SAN representing the amorphous components, have been studied by small angle X-ray scattering. For both blends the long period increases with the addition of amorphous polymer, which is a strong indication for an interlamellar morphology. D.s.c. experiments, including enthalpy relaxation, are used to investigate the crystallinity and the interphases. The overall amount of crystallinity in both blends decreases with increasing content of amorphous polymer. However, the fraction of PCL that crystallizes decreases in PCL/SAN and increases slightly in PCL/PVME. Apparently, the addition of the low T~,, PVME improves the crystallization of PCL in accordance with a simple Gamblers Ruin Model type argument. The high Tg,a of SAN means this does not occur in PCL/SAN blends. Conventional d.s.c. experiments show an interphase of pure amorphous PCL in PCL/SAN blends and enthalpy relaxation experiments demonstrate its presence in PCL/PVME blends as well.

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The mechanical properties and phase morphology of blends of nylon-6 with various acrylonitrile-butadienestyrene (ABS) materials and compatibilizers are explored. The main focus was on nylon-6/ABS blends compatibilized with one particular imidized acrylic polymer that is miscible with the styrene-acrylt~aitrile (SAN) matrix of the ABS and has nearly optimal content of functional groups (anhydride and free acid) for reaction with nylon-6 to form graft copolymers in situ at the polymer-polymer interfaces. The effects of compatibilizer content, rubber concentration and the mixing protocol on the mechanical properties of these blends were extensively explored. In general, the most efficiently dispersed ABS domains in the nylon matrix led to the lowest ductile-brittle transition temperatures and the maximum tensile modulus for the super-tough nylon-6/ABS blends. The effects of varying the functionality and miscibility characteristics of imidized acrylic polymers on the mechanical properties and morphology of nylon-6/ABS blends were also investigated. Some other types of polymers with a high anhydride content were also tested as compatibilizers for this system. It appears that compatibilizers with high levels of reactive functinality are not very effective; hence, there is an optimal level of functionality.

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The morphology of extruded pellets, compression and injection moulded articles, and melt spun fibres of a random liquid crystal terpolymer has been investigated. Etching and self-decoration techniques have been used, which reveal a lamellar morphology in bulk samples. The lamellae, ranging from 50 to 1800 A in thickness depending on the preparation technique, are oriented perpendicular to the fibre or extrusion direction in melt spun fibres and extruded pellets. Extruded pellets are analogous to a composite material with 0.2-1.8 #m diameter 'fibres' of the liquid crystal being embedded in a less oriented matrix; greater alignment of the lamellae is observed in the 'fibres'. The thickness of the lamellae observed in melt spun fibres ranged from 500 to 800A. Thinner lamellae (50-130A) are observed on the surface of compression moulded specimens with thicker (200-1800A), presumably extended chain lamellae in the interior. The thickness and degree of alignment, or order, of the lamellae is dependent on the cooling rate. Selected area electron diffraction confirms that the chain axes are perpendicular to the lamellae.

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The composition and monomer unit sequence distributions of copolymers of styrene with citraconic (ct-methylmaleic) anhydride (CA) prepared in methyl ethyl ketone at 50.0___0.1°C have been determined over a range of comonomer feed mole fractions using 13 C n.m.r, spectroscopy. The monomer units in these copolymers were found to display an increasingly strong tendency to alternate as the mole fraction of CA in the feed increased. The terminal, penultimate, complex-participation and complex-dissociation models were each tested for applicability to the mechanism of copolymerization for this comonomer system by applying reactivity ratio related test functions to the experimental sequence distribution data, enabling a direct visual assessment of the applicability of each model to be made. On the basis of these test functions, the terminal, penultimate and complex-dissociation models were each found to provide inadequate descriptions of this copolymerization system

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The crystalline polyamide phase in two representative poly(ether-block-amide) copolymers has been shown to be polymorphic in nature via an analysis by X-ray diffraction and solid-state ~3C nuclear magnetic resonance. In both polymers, this phase was found to adopt ~t and ;, structures analogous to those that exist in the corresponding polyamide homopolymers. Furthermore, it has been shown that phase transformation between crystal types is possible using chemical modifications

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The mechanical properties and phase morphology of compatibilized blends of acrylonitrile-butadienestyrene (ABS) with a wide range of polyamide materials having different physical and chemical characteristics were explored. The most efficient dispersion of the ABS phase and the best combination of mechanical properties occur within an optimum range of the nylon/ABS viscosity ratio. It is significantly more difficult to disperse the ABS and to generate toughened blends when the polyamide material is difunctional in character, i.e. a fraction of the chains having two amine end-groups. Increasing the inherent ductility of the polyamide leads to improved toughness of these blends.

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Convergence-accelerating methods have been applied to series expansions for the stable-law density Q,(z)=~foe-"=cos(zu)du which is, in turn, simply related to the spectral density of the Kohlrausch-Williams/Watts (KWW) decay function q~(t)--e-lt/~)=]. N.m.r. relaxation parameters such as NOEF, T1 and Tip are computed for polycarbonate and polydimethylsiloxane using the new series and the results compared to experiment and to earlier computations which employed a decomposition of the KWW function into a sum of exponential terms.

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The effect of high pressure up to 2500 bar on the chain motion in amorphous chain-deuterated polyethylene is studied in a wide range of temperature (203-393 K) using the deuteron nuclear magnetic resonance (2H n.m.r.) quadrupole echo and spin alignment echo technique. Quadrupole echo spectra simulated on the basis of Flory's rotational isomeric state model appear to reproduce the experimental spectra quite well. The comparison yields information on the time-scale of the motion. The temperature dependence of the mean correlation time shows an Arrhenius behaviour in the temperature range from 223 to 383 K. The activation energy at ambient pressure is 11.3 kJ mol- 1, which is slightly lower than the value of the barrier between the trans and gauche conformations (13.2 kJ mol- 1). The effect of increasing the pressure by 1 kbar corresponds roughly to lowering the temperature by 15 K.

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Blends consisting of a polyamide 66 (PA) matrix (75 wt%) and a dispersed isotactic polypropylene (PP) phase were prepared by extrusion with anhydride-grafted isotactic polypropylene compatibilizers, one of high anhydride content (HAC, 2.7 wt% grafted maleic anhydride) and one of low anhydride content (LAC, 0.2 wt% grafted anhydride). HAC and LAC had similar effects on PP domain size and tensile properties at equal loadings, unlike the anhydride concentration dependency that had been reported for high PP content blends. As compatibilizer loading increased from 0wt% to 7.5 wt%, a skin/core injection-moulded morphology gradient diminished, PP domain size decreased to less than 1/~m, tensile strain increased and microscale deformation of the PP phase progressed from debonding to particle drawing and debonding to fibril fracture. The PP phase deformation mode depends on the interfacial strength as compared to the PP domain strength. HAC and LAC are postulated to behave similarly because of sufficient reactivity with PA and similar surface coverage by HAC-g-PA and LAC-g-PA. Interfacial strength is postulated to increase with decreasing particle size because of increasing surface/volume ratio at relatively constant surface coverage

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