1992 рік

Tetrahydropyranyl (THP) protected poly (p-hydroxystyrene) (PHS) was synthesized and its acid-catalysed thermal deprotection utilized in the design of an alkali developable, positive phOtoresist system incorporating chemical amplification. The solubility of THP-PHS films mixed with the appropriate onium salt photo acid generators in alkaline developers increases upon exposure to deep u.v. radiation and subsequent heating. A resist composed of THP-PHS and bis(tert-butylphenyl)iodonium triflate resolves 0.35/~m line-and-space patterns using a KrF excimer laser (248 nm) stepper (20 mJ cm 2).

Детальніше...  

Copolymers incorporating rigid electroactive moieties and flexible segments have been synthesized in an effort to develop non-linear optical materials which can be processed into optical quality films. A variety of coupling linkages have been employed including ether, ester, amide, imine and azo linkages. Among the most attractive materials examined in this survey are heteroaromatic ladder and tetraazaannulene copolymers which yield optical non-linearities (ratioed to optical loss), Z(3)/ct, of 10 -12-10-13 esu cm-1 and have desirable auxiliary properties of high laser damage threshold and fast optical switching (5 ps for three-ring copolymer). Electron donating and withdrawing groups are conveniently incorporated and these have been observed to influence optical non-linearity. The copolymer approach yields linear optical spectra characterized by sharp band edges thus optimizing the window of transparency. Finally, it is noted that this approach yields excellent control of solubility and solution viscosity necessary for spin casting in the fabrication of thin films of uniform thickness.

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Polyesters from dimethyl terephthalate, ethylene glycol, poly(ethylene glycol) and 4,4’-bis(carbomethoxy)- stilbene were synthesized via a thermal transesterification reaction. The assignment of proton frequencies was facilitated by 2-D n.m.r. techniques. The presence of ethyl01 end groups and the occurrence of a cis to tram stilbene monomer isomerization were observed and are reported herein

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E.p.r. relaxation measurements have been made on polymers derived from poly (vinyl alcohol ). Poly (vinyl alcohol) was esterified with three carboxylic acids, one of which was bifunctional, leading to formation of a polymer network. Polymeric samples were studied with two nitroxide sonds and a nitroxide label copolymerized in the main chain. The label had longer correlation times than the sonds. However, the activation energy calculated for the rotational diffusion of the label was lower than that for the radical sonds. In the linear polymers, the size of the side group affected only slightly the rotational motion of the sonds, whereas the rate of motion of the label was very sensitive to variations in the side group.

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Polymer radicals derived from diethyl, diisopropyl, dicyclohexyl and di-tert-butyl fumarates were spin-trapped with 2,4,6-tri-tert-butylnitrosobenzene (BNB), which yields an anilino radical and a nitroxide depending on the steric environment of the radical centre. The spin adduct was prepared by fumarate polymerization initiated with di-tert-butyl hyponitrite in the presence of BNB and by the reaction with active poly (fumarate) radical. According to the e.s.r, spectra of the spin adducts, increases in the bulkiness of the ester alkyl group and the polymer chain length brought about a larger quantity of the anilino radical. This finding indicates the tendency that the reactivity of poly (fumarate) radical toward BNB is differentiated by the steric hindrance caused by the polymer chain and the ester alkyl group

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Immiscibility has been confirmed by noting two glass temperatures for blends of two polyimides, a poly (ether imide) and a poly(amide imide). Phase diagrams provided here show how this pair can be compatibilized to show only a single glass transition by the addition of sulphonated PEEKs.

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We have successfully developed a two-stage self-seeding technique to grow poly (phenylene sulphide) (PPS) single crystals from dilute solution, and used these single crystals as model materials to investigate the morphological changes dependent upon the seeding and crystallization conditions. The seeding conditions control the coexistence of different crystal types and determine whether isolated single crystals will be grown. The crystal Structure and morphology of PPS single crystals have been investigated by using the wide angle X-ray scattering (WAXS) and transmission electron microscopy techniques including surface decoration by polyethylene. The morphology of the PPS single crystals reveals a highly anisotropic needle-like habit with a very smooth fold surface and very rough growth edges. The aspect ratio of the PPS needle-like single crystals increases as the crystallization temperature and molecular weight increase. Formation of needle-like crystals, lack of sectorization, formation of macroscopically rough growth surfaces, and molecular weight and crystallization temperature dependency of crystal habit suggest a crystal growth model in which the PPS molecules fold parallel to the growth direction during the crystal growth stage from dilute solution.

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Reactive polyamides with amine values ranging from 310 to 389 were prepared by reacting C 21 cycloaliphatic dicarboxylic acid, prepared from acrylic acid and dehydrated castor oil fatty acids, with various polyamines, namely diethylenetriamine, triethylenetetramine and tetraethylenepentamine. Some reactive polyamides of matching amine values were also prepared by using C36 dimer acids and tetraethylenepentamine for comparison. The polyamides were then reacted with an epoxy resin (epoxy resin of equivalent weight 450) in different equivalent weight ratios. The cured product obtained by using an equivalent weight ratio of 1.00:1.00 of epoxy resin and reactive polyamide had better binding properties in comparison to other binders. The binders derived from C21 dicarboxylic acid were better than those derived from C36 dimer acids in both adhesion and hardness, and were superior in tensile strength.

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Interfacial adhesion and toughening mechanisms in an alloy of polycarbonate/polyethylene (PC/PE) are investigated using transmission electron microscopy. In contrast to the general speculation, it is found that the PE particles strongly adhere to the PC matrix. The toughening mechanisms in the PC/PE blend are found to be debonding of the PC/PE interface, which relieves the triaxial tension in front of the crack tip, followed by shear banding of the PC matrix. Possible causes for such an unexpected strong interfacial adhesion between PC and PE are discussed. Also, the importance of the cavitational strength of the toughener phase in toughness optimization is addressed.

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Axial tensile moduli, compressive moduli and compressive strengths of rigid-rod poly(p-phenylene benzobisoxazole) and stiff-chain poly(p-phenylene terephthalamide), Kevlar TM, fibres were measured with a Tecam Micro-tensile Testing Machine. This machine was configured to allow for testing of single fibres in direct tension and compression at extremely small gauge lengths. The appropriate gauge lengths were estimated based on the discussion of Euler buckling and non-uniform stress distribution in anisotropic materials. The measured tensile and compressive moduli were analysed for corrections to machine compliance and possible gauge length error. The corrected compressive moduli were slightly lower than the corrected tensile moduli, probably due to fibre misalignment under compression and the fibrillar nature of the fibres. The fibre axial compressive strengths measured by direct compression were comparable to those measured from recoil and composite tests but lower than those from cantilever beam and elastica loop tests.

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