Analysis of polyurethanes using core excitation spectroscopy. Part I: Model polyurethane foam polymers

The C 1s, N 1s, and O 1s excitation spectra of model methylenediphenyldiisocyanate (MDI) polyurethanes with well known structures have been recorded using electron energy loss spectroscopy (EELS) in an electron microscope. These spectra are compared to the core excitation spectra of selected small molecule analogue species (recorded by gas phase EELS) in order to identify transitions characteristic of various structural components found in polyurethanes. A more detailed report on the small molecule analogue spectra is presented in the following article. Spectral features characteristic of the different structural components in polyurethanes are identified in the spectra of the model polymers. These can be used as the basis for chemical studies of micron or submicron sized segregated phases in flexible polyurethane polymers. © 1995 John Wiley & Sons, Inc.     

Preparation and characterization of N‐methyl‐substituted polyurethane

We prepared N‐methyl‐substituted polyurethanes with different substitution degrees from sodium hydride, methyl p‐toluene sulfonate, and polyether–polyurethane containing poly(oxytetramethylene) glycol, 4,4′‐diphenylmethane diisocyanate, and 1,4‐butanediol. The chemical structures were characterized with Fourier transform infrared and ¹H NMR. To investigate the effects of the N‐substitution degree on the morphology, thermal stability, and mechanical properties, we used differential scanning calorimetry, thermogravimetric analysis, and a universal testing machine. As the substitution degree increased, the new free (1708 cm^?1) and bonded (1650 cm^?1) carbonyl peaks increased. There was no bonded carbonyl peak in fully substituted polyurethane because the urethane groups had no hydrogen. At a small substitution degree, we observed a slight increase in the glass‐transition temperature and decrease in the endotherms of soft‐segment and hard‐segment domains due to the decrease in the hard‐segment domain and the increase in the urethane groups in the soft‐segment domain. The hard‐segment domain decreased and then disappeared as the N‐methyl substitution degree increased. These changes in the morphology resulted (1) in decreased modulus and tensile strength for the films because of the decrease in physical crosslinking points and (2) improved thermal stability as the substitution degree increased. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4077–4083, 2002     

Synthesis,Characterization and Properties of Novel Poly(Ester-Amide-Urethane)s

A diacid (TOBA) containing an ester group was synthesized by reaction of terephthaloyl chloride with 4-hydroxybenzoic acid. Reaction of the obtained diacid with thionyl chloride resulted in preparation of the related diacid chloride (TOBC). Nucleophilic substitution reaction of 4-aminophenol and also 5-amino-l-naphthol with the prepared diacid chloride afforded two aromatic diols containing ester and amide groups, respectively. Aromatic and semi-aromatic poly(ester-amide-urethane)s were prepared via addition polymerization of different diisocyanates with novel diols. The prepared polyurethanes showed improved thermal stability.     

生物降解型聚氨酯研究进展

本文综述了生物降解型聚氨酯的研究现状，并探讨了影响其生物降解性的因素，指出了其应用前景，特别是医学上的应用．     

THERMALLY STIMULATED SHAPE MEMORY BEHAVIOR OF POLYMERS WITH PHYSICAL CROSSLINKS*

The shape memory effect of polymers was investigated for the purpose of improving the processingconditions of their preparation and broadening the list of polymers for shape memory applications. Emphasiswas put on the possibility of using polymers with physical crosslinks as shape memory materials and theirstructure-function relationships. Segmented block polyurethanes and polyethylene/nylon 6 graft copolymerswere used as examples of polymers with physical crosslinks. It was found that these copolymers can really beused as thermally stimulated shape memory materials with large recoverable strain and high final recoveryrate. The main advantage of using copolymers is their improved processing conditions as compared withpolymers with chemical crosslinks. As only physical crosslinks are introduced, all conventional processingtechniques for thermal plastics can be used, and the materials become easily reusable. The results indicatethat the high crystallinity of these copolymers at room temperature and the formation of stable physicalcrosslinks are the two prerequisites for these polymers to exhibit shape memory effect. The successful use ofblock and graft copolymers imply the possibility of using polymers of various structure and properties asshape memory materials.     

Hyperbranched polyurethanes with varying spacer segments between the branching points

Hyperbranched polyurethanes, with varying oligoethyleneoxy spacer segments between the branching points, have been synthesized by a one-pot approach starting from the appropriately designed carbonyl azide that incorporates the different spacer segments. The structures of monomers and polymers were confirmed by IR and ¹H-NMR spectroscopy. The solution viscosity of the polymers suggested that they were of reasonably high molecular weight. Reversal of terminal functional groups was achieved by preparing the appropriate monohydroxy dicarbonyl azide monomer. The large number of terminal isocyanate groups at the chain ends of such hyperbranched macromolecules caused them to crosslink prior to its isolation. However, carrying out the polymerization in the presence of 1 equiv of a capping agent, such as an alcohol, resulted in soluble polymers with carbamate chain ends. Using a biphenyl-containing alcohol as a capping agent, we have also prepared novel hyperbranched polyurethanes with pendant mesogenic segments. These mesogen-containing polyurethanes, however, did not exhibit liquid crystallinity probably due to the wholly aromatic rigid polymer backbone. © 1996 John Wiley & Sons, Inc.     

Synthesis of a fluoro-diol and preparation of fluorinated waterborne polyurethanes with high elongation at break

In this study, a fluoro-diol, trifluoroethyl-2-methylpropanoate-β-dihydroxy ethylamine (TFMDA), was successfully synthesized by Michael Addition reaction between trifluoroethyl-2-methacrylate (TFEMA) and diethanolamine (DEA). The chemical structures were characterized by FT-IR and ¹H NMR methods. And then by the reaction of dicyclohexylmethylmethane-4,4′- diisocyanate (HMDI), poly(propylene glycol) (PPG), 2,2-dimethylolbutanoic acid (DMBA), diethylene glycol (DEG) and trifluoroethyl-2-methylpropanoate-β-dihydroxyethylamine (TFMDA), fluorinated waterborne polyurethane emulsions with different content of COOH and TFMDA were successfully prepared. It was demonstrated that all the polyurethane emulsions exhibited enhanced storage stability and all the polyurethane films possessed high elongation at break and exceeded 1000%. Addition of organic fluorine obviously improved the water-resistance property of the waterborne polyurethane films.     

Different catalytic systems on hydroxyl-terminated GAP and PET with poly-isocyanate: Curing kinetics study using dynamic in situ IR spectroscopy

Reactions of hydroxyl-terminated glycidyl azide polymer (GAP) or poly(ethylene oxide-co-tetrahydrofuran) (PET) polymers with poly-isocyanate (N100) were monitored by dynamic in situ Fourier transform infrared spectroscopy. The influence of catalytic systems on the cure kinetics of polyurethane reaction was investigated. From the comparison between GAP/N100 and PET/N100 systems, it was found that primary and secondary hydroxyl groups were differentiated due to the effects of steric hindrance. Using Arrhenius law and Eyring equation, the activation parameters of polyurethane reaction were calculated at different catalytic systems. The negative value of the activation entropy demonstrated an associative mechanism within the transition state.