1992 рік

tert-Butoxycarbonylated, fractionated cresol-formaldehyde novolac (tBOC-N) was investigated as a dual-tone, chemically amplified, deep-u.v, and electron-beam resist. The protected polymer is highly transparent at 2 > 240 nm, and thermally stable up to 170°C. Negative-tone, 75-nm line-and-space patterns were obtained in the tBOC-N-based resist by electron-beam lithography. The deprotected novolac was insoluble in aqueous bases, possibly because of acid-catalysed alkylation reaction.

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A wholly aromatic copolyester having an ordered comonomer sequence was prepared from 2,7- naphthalenediyl bis(4-hydroxybenzoate) and terephthalic acid following a method reported previously• This polymer was subjected to thermal treatment at 305°C under nitrogen atmosphere and the sequence randomization process was quantitatively analysed by 13C n.m.r, spectroscopy• The melting temperature of the original polymer was 290°C. According to the results of analysis for various triad formation, the ester bonds in the triad of terephthaloyl-p-oxybenzoyl-oxynaphthyleneoxy (TPN) sequence were found to undergo very fast exchange reactions at the treatment temperature. The formation of PPP triad was evident after 30 min at 305°C, whereas PP dyad was formed after only 10 min. Although the sequence' changes occurred rather rapidly, complete randomization was not attained even after 1 h

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Pyrograms of poly(2,6-dimethyl-l,4-phenylene ether) (PPE) samples were obtained by on-line high resolution pyrolysis-gas chromatography (HR-Pyg.c.). Characteristic peaks on the pyrograms (up to trimers) were assigned by using gas chromatography mass spectrometry (g.c.-m.s.) and retention time data. The analysis of a series of fractions of varying molecular weight from a given PPE sample suggested that HR-Pyg.c. would be a powerful technique for characterization of the end groups of PPE when t3C-n.m.r, was used to take reference data for these end groups.

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The state of various alcohols with carbon numbers from one to eight in a poly (dimethylsiloxane) (PDMS) membrane was investigated by d.s.c. Methanol, ethanol, 2-propanol, 1-butanol and 1-pentanol were present in the PDMS membrane in the bound state as well as in the bulk state, while 1-octanol was comprised only of free 1-octanol. The amount of bound alcohol increased with increase in the carbon number up to four and then decreased with further increase in the carbon number. We concluded that the interaction between the methyl group in the PDMS membrane and the alkyl moiety in the alcohol was a specific interaction to form bound alcohol in the PDMS membrane.

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A series of blends has been prepared by adding a polyetherimide, in varying proportions, to a trifunctional epoxy resin, triglycidylparaaminophenol, cured with 4,4'-diaminodiphenylsulphone. All the materials showed two-phase morphology when characterized by dynamic mechanical thermal analysis and scanning electron microscopy. Addition of the thermoplastic resulted in improved fracture properties (Klc and G lc), as measured by three-point bending experiments, although no obvious correlation with blend morphology was observed

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A number of di- and triacrylates and methacrylates containing silicon have been prepared. In the presence of a photoinitiator and absence of a tertiary amine, these compounds photopolymerized to give thin films, and in some cases this was not accompanied by shrinkage. The rate of polymerization, as judged by the amount of exposure to give tack-free coatings, was usually found to be much greater than standard diluents such as hexanediol diacrylate, tripropyleneglycol diacrylate and trimethylolpropane triacrylate. Monitoring the degree of cure by quantifying the extent to which the acrylate or methacrylate groups have been utilized showed that the presence of silicon affected the extent to which double-bond utilization occurs.

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Solutions of poly(N-isopropylacrylamide) (polyNIPAAm) become turbid at their lower critical solution temperature (LCST) of 33°C. In this study we have conjugated a phospholipid, 1-acyl-2-{ 12-[(7-nitro- 2-1,3-benzoxadiazol-4-yl)amino]dodecanol}-phosphatidylethanolamine, to polyNIPAAm. Conjugation increases the LCST of polyNIPAAm by ~ 2°C and broadens the temperature range over which turbidity changes. Conjugation of phospholipids to polymers in general and to thermally reversible polymers in particular may allow some novel applications that relate to their potential for insertion into liposomes, micelles or cell membranes and hydrophobic interfaces.

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Polyurethanes (PUs) were prepared by using diols containing polar groups such as carbonic groups -O-COO-, carbonic and ester --COO- groups, carbonic and ether -O- groups. Synthesis and film preparation conditions are given. The physical properties of the PUs such as density, glass transition temperature, Tg, melting point, Tin, are all presented. A correlation between T~ and the rotational energy barriers of the polydiol single units is discussed. The PUs were characterized by mechanical tests on dry samples. The crosslink density of the PU network was evaluated by mechanical equilibrium relaxation tests on samples swollen in toluene. The results are discussed according to the more recent Flory's theory of rubber elasticity. PUs containing a CO3 group present an affine-like behaviour while PUs containing both CO3 and ether or ester groups show a behaviour in between affine and phantom models.

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A series of silicon-containing mono-, di-, tri- and tetraacrylates have been synthesized. The tetraacrylates and triacrylates cure at very low doses to give hard, flexible films possessing good solvent resistance properties. The diacrylates cured rapidly to give soft films, whereas the monoacrylates polymerized to give highly viscous fluids. A quantitative evaluation of rate of cure showed that the order of reactivity was diacrylate > triacrylate > monoacrylate. The presence of silicon appears to confer many special properties. These are ascribed to the silicon atom effecting enhanced conformational mobility of the polymer chains. The high reactivity of the di- and triacrylates may be due to the silicon acting as a site for ionization, leading to the production of initiating species.

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The transport and diffusion properties observed for solid n-alkanes and the premelting phenomena in polymethylene systems imply that molecular chains possess conformational flexibility coupled to longitudinal mobility. Most of the authors have proposed models based on the creation and mobility of conformational kinks whose existence is not proven by spectroscopy. The existence of 'twistons' has been postulated. In this work vibrational i.r. and/or Raman spectroscopy is used as a probe for twistonic excitations. The conditions for the spectroscopic observation of twistons are discussed. The temperature dependence of the spectra of n-alkanes from the orthorhombic to '~' (or 'pseudohexagonal') and to melt phases is studied and the spectra are interpreted in the attempt to find evidence of twistons. As a test case of the theoretical predictions the spectra of n-alkanes in urea clathrates are discussed. Indications are found that twistons start being produced while still in the orthorhombic phase when the lattice starts expanding. The '~' phase (or premelting state) may be considered as a 'soft' phase consisting of a collection of twistonic chains out of register because of the propagation of twistons which also generate the spectroscopically observed surface disordering and diffusion.

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