ABSTRACT:BC solid state high resolution NMR spectra of ultra high-molecular weight polyethylene fibers (UHF) were measured. The main narrow line is due to orthorhombic crystalline phase (ORC). Because of the high degree of crystallinity, amorphous phase signal is observed so small as the foot of the main crystalline phase signal. The small signal of monoclinic crystal phase (MCC) can be observed at lower field than the ORC signal. Signal width of MCC peak is as narrow as ORC peak. Several kinds of relaxation parameters are measured to discuss the two crystalline and intermediate phase. The crystalline phase signal can be divided into several components according to the difference in relaxation time. The signal of highly mobile component spreads over MCC and ORC signals. This component is not a crystal but its conformation is similar to that of the crystal. It may be such as oriented amorphous.

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Several kinds of model compounds for anomalous linkages in polyurethanes (branching or crosslinking; allophanate and biuret) were prepared. The phenylisocyanate (PHI) based models were identified by IR and NMR. The 13C‐NMR chemical shifts effects due to the anomalous linkages were determined. The 4,4′‐diphenylmethane diisocyanate (MDI) based models were purified incompletely but the characteristic signals of the aromatic carbons were nevertheless found in their spectra. Two types of segmented polyurethane (SPU) were prepared and the anomalous linkages were investigated by 13C‐NMR. The signals due to the allophanate (Al) and the triphenylbiuret (TB) linkages were observed in the spectra of the SPU prepared at high temperature (>80°C) or prepolymer gels yielded by abnormal reaction. A small signal due to a phenyl carbon of biuret (Bi) linkage was observed even in a normally prepared SPU (polyetherurethane‐urea). Employing the phenyl carbon signals was advantageous for the determination of anomalous linkages because of their larger intensities.

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Effect of acid acceptor (AA) on the low temperature solution polymerization of the copolyamide 4I-PIP(20) from isophthaloyl chloride, 4,4Ј-diaminodiphenylsulfone, and piperazine (their diamine component ratio is 80 -20) was studied. The type and amount of AA had a large effect on not only the polymerization condition and polymerization degree of 4I-PIP(20), but also on its microstructure. Pyridine was the most favorable AA, since it gave a homogeneity to the polymerization solution of 4I-PIP(20), and that it was most suitable for the synthesis of 4I-PIP (20) with high polymerization degree. The H-NMR measurement made it clear that 4I-PIP(20) prepared with pyridine was random copolyamide.

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ABSTRACT:Segmented polyurethane-urea (SPU) elastomer was prepared from polytetramethyleneglycol (PTMG), 4,4'-diphenylmethane diisocyanate (MDI), and ethylenediamine (EDA). The SPU is a kind of block copolymer composed of soft and hard segments. 13 C NMR spectra of the SPU were measured and the mean sequence lengths of polyurethane block and polyurea block were estimated from the signals of aromatic carbons. The mean polyurea sequence length was shorter than the hard segment as estimated by X-ray diffraction (Kimura et al.) or by other methods (Suzuki et al.). This polymer was found to be almost a random copolymer. The reactivity of the isocyanate group in MDI decreases slightly when the other side of isocyanate has reacted. The hard segment observed by X-ray diffraction or by other methods might only be the longer fraction of polyurea sequences.KEY WORDS Polyurethane-urea / Sequence Distribution / Isocyanate / 4,4'-Diphenylmethane Diisocyanate / Reactivity Ratio/ 1 3 C NMR / Segmented polyurethane-urea (SPU) elastomer is a kind of block copolymer composed of soft and hard segments. The soft segment usually consists of aliphatic polyether or polyester urethane block and the hard segment is a polyurea block. SPU is usually prepared in two-stage reactions as shown in Figure I. A diisocyanate compound is reacted with a hydroxy terminated prepolymer (I). The amount of the isocyanate compound exceeds that of prepolymer (I) so that the unreacted isocyanate compound remains after the reaction. The resultant polymer (prepolymer (II)) is then extended with a diamine (chain extender). The mechanical properties of SPU depend on (l) the composition of soft and hard segments, (2) the length of soft and hard segments, or in other words, the molecular weight of prepolymer (I) (polyether or polyester) and the sequence length distribution, (3) anomalous linkages (branching, crosslinking), (4) molecular weight of SPU. The hydrogen-bonding in the crystal of the hard segment plays important roles in the elasticity of this polymer. 1 -3 The estimation of the lengths of soft and hard segments is essential for the investigation of SPU. Kimura et al. observed the length of hard segment directly by wide angle X-ray diffraction and by small angle X-ray scattering when the chain extender was 4,4'-diphenylmethanediamine (MDA). 4 · 5 They estimated the length of the hard segment composed of the polyurea block to be about four monomer units in the case of the molar ratio of prepolymer (1)/chain extender= 1 : 1. Suzuki et al. measured the length of the polyurea block in a similar SPU (chain extender; hydrazine) by selective degradation. 6 The length of the polyurea block agreed with the length of the hard segment estimated by Kimura et al. This suggests that the polyurea block is identical to the hard segment.The length of polyurea block depends on the reactivity ratio of isocyanate groups of diisocyanate compounds. 7 In the case of 4,4' -diphenylmethane diisocyanate (MDI), the re-1065

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