1999 рік

High performance properties are increasingly needed in fibers for industrial applications. Such properties have been achieved in both flexible and intrinsically stiff polymers, but only through specialized and expensive spinning methods. In this work, the potential of achieving high performance mechanical behavior in nylon 6 using a conventional spinning process was explored. We report the formation of highmolecular-weight polymer inclusion compounds (ICs) between a- and b-cyclodextrins (a- and b-CDs) and nylon 6 (M n ¼ 12 kg mol ¹1). Both high-molecular-weight polymer ICs were successfully made by a heating technique. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), wide-angle X-ray diffraction (WAXD), and Fourier transform infrared (FTIR) spectroscopy have been utilized to observe the nylon 6 polymer chains included inside the channels formed by the cyclodextrins. DSC and TGA scans showed the hightemperature stable nylon 6-CD-IC samples contain no free crystalline nylon 6 polymer, and the much higher decomposition temperatures observed for these nylon-CD-ICs may imply that polymer chains included inside the polymer CD-IC channels can greatly improve cyclodextrins’ stabilities. The nylon 6-a-CD-IC and nylon 6-b-CD-IC X-ray diffraction patterns were very similar to those of valeric acid-a-CD-IC and 1-propanol-b-CD-IC, which were confirmed to be channel crystal structures by single crystal X-ray diffraction. A new band which was absent from the pure cyclodextrin spectrum appeared at 1729 cm -¹ for nylon 6-CD-ICs in their FTIR spectra and may be characteristic for CDs in their channel-forming ICs.

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In this work, semi-empirical quantum mechanical techniques were employed in order to discuss the feasibility of the copolymerization reaction between tetrahydrofuran and pyrrole starting from two different macromonomers in which polytetrahydrofuran has a pyrrole moiety at one or both ends.

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Several alternating and semi-alternating copolymers were analysed by quaternary 13C n.m.r. spectroscopy. The aromatic 'next to polymer chain’ carbon (C7) of donor monomer (1) units is sensitive to the unit 1-centred triad sequence distribution. The acceptor monomer is referred to as 0. The chemical shifts of the non-alternating (111), semi-alternating (011 þ 110) and alternating (010) triad sub-peaks were assigned in ppm in Table 1.

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Pure gas transport properties of natural rubber (NR), epoxidised natural rubber (ENR) and their blends have been determined. The permeabilities of the pure polymers and blends were determined with nitrogen and oxygen. The relation between oxygen-to-nitrogen selectivity and the glass transition temperature has been studied. NR is more permeable to nitrogen and oxygen but ENR-50 shows maximum oxygen-to-nitrogen selectivity. In NR/ENR blends, permeability of the penetrant decreases with volume fraction of ENR, whereas selectivity increases with volume fraction of ENR. Pure gas permeabilities of NR/ENR blends were compared with models for permeation in heterogeneous media.

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The morphological changes occurring during the phase inversion of a polystyrene/polyethylene blend subjected to isothermal, steady shear flow are investigated and characterized. The isothermal, steady shear flow field provides a well-defined thermal and flow history. This contrasts with previous work on phase inversion, which was conducted in complex flow fields with large temperature gradients. The welldefined flow field permits a more detailed examination of the sequence of morphological changes during phase inversion than was accomplished previously. Both components are observed to initially deform into a sheet morphology. At strains of 200–780, the (initially continuous) minor component begins to break up, allowing the (initially dispersed) major component to coalesce. The blend becomes cocontinuous around strains of 330–1500. At strains of 500–2000, the major component continues coalescing. The minor component breaks up into fibers and drops at strains of 800–3000. Breakup of the minor-component sheets is not observed until the sheets are less than 1 mm thick. Deformation and breakup of the initially dispersed phase is observed in this shear flow field, despite a viscosity ratio in excess of 10. For the system studied here, phase inversion does not occur under no-flow conditions.

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A new chemically amplified resist containing a basic monomer, 3-(t-butoxycarbonyl)-1-vinylcaprolactam, in the matrix polymer was prepared for post-exposure delay stability. Poly(3-(t-butoxycarbonyl)-1-vinylcaprolactam-co-t-butyl methacrylate) was synthesized and evaluated as a new matrix resin. The diffusion lengths of photogenerated acid in the resist films were studied for various fractions of the basic monomer in the copolymers. The results show the copolymer with a basic monomer can control the acid diffusion without a severe decrease in sensitivity. This new resist system enables us to form fine patterns and attain 2 h post-exposure delay stability without any additional treatment.

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Functional polyisoprene stars were prepared by copolymerization of polyisoprenyl lithium with divinylbenzene in n-heptane, where the polyisoprene arm was prepared by anionic polymerization using [2-[N,N-dimethylamino)methyl]phenyl]lithium as the initiator. The star polymer was removed from the unreacted arms. These functional stars were converted by quaternization with p-chloromethylstyrene into polyisoprene star-shaped macromonomers having ca. one vinylbenzyl group at each arm end.

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Plasma polymerised acrylic acid (ppAAc) coatings were deposited on aluminium substrates from acrylic acid plasmas at various plasma powers (P). The chemistry of the ppAAc deposit was characterised using X-ray photoelectron spectroscopy (XPS) and trifluoroethanol derivatisation of the carboxylic acid functionalities. The absorption of atmospheric moisture by ppAAc was quantified using a vibrating quartz crystal microbalance. The solubility in ethanol, water and hexane of ppAAc deposited on aluminium was investigated using substrate signal attenuation in XPS. The high carboxylic acid concentrations retained in the low P deposits correlates with a hydrophilic ppAAc coating, i.e. they are readily soluble in water and absorb moisture from the atmosphere. The lower carboxylic acid content and greater crosslinking of coatings produced at higher P result in less hydrophobic deposits which are resistant to rinsing with water. Addition of 1,7-octadiene vapour to a P ˆ 2 W acrylic acid plasma produces insoluble plasma polymerised acrylic acid-co-1,7-octadiene (ppAAc-co-Oct) deposits. A carboxylic acid containing fraction of these insoluble coatings is removed by hexane rinsing which we propose is physisorbed oligomer. We propose that slow evaporation of these oligomers is responsible for the decrease in the acidity of the coatings observed over time under atmospheric storage. The contact angle of water insoluble coatings is measured as a function of time after a water drop is placed on the surface. An initial fast decrease of the contact angle was observed which is consistent with a rapid absorption of water into the plasma polymer. A low contact angle/ high wettability correlates with coatings determined to have high carboxylic acid concentrations. By changing the ppAAc-co-Oct chemistry a change in the contact angle of 408 can be achieved.

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The effects of crystallinity, lamellar thickness and stem length on the yield behaviour of a range of bulk crystallized and pressure annealed polyethylenes have been analysed. The materials studied differ greatly with respect to lamellar thickness, stem length and the degree of crystallinity. Measurements of the yield stress were carried out at 60°C and at a strain rate of 3.5 х 10 ¹3 s ¹1, where the materials are known to exhibit elastic–plastic deformation. The results show that, under these conditions, the yield behaviour is a nucleation-controlled process which is accurately modelled in terms of crystal plasticity, with the yield stress being determined by the stem length of the chains in the crystalline lamellae. Detailed measurements of the stem length and crystallinity have shown that, for these materials, there is an interrelationship between the crystallinity and the stem length. This interrelationship, combined with the crystal plasticity model, leads to the prediction that the yield stress increases as a power-law relationship with crystallinity.

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The high electron affinity conjugated polymer, poly(2,5-pyridinediyl) (PPy), can be used as the electron-transport/hole blocking layer in a light-emitting diode with poly(phenylene vinylene) (PPV) as the emitting layer, ITO as the anode and aluminum as the cathode. The incorporation of PPy layer provides an improvement in the conversion efficiency of current density to brightness by a factor of 17.

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