For high-tech applications, polyurethane (PU) materials require additional surface properties and functionality, which can be achieved by incorporation of "clickable" groups in the PU structure, allowing for polymer post-modification via chemical coupling with desired molecules. Therefore, in this study, various "click" and coupling reactions, consisting of the copper(I) catalyzed Huisgen 1,3-dipolar alkyne-azide, thermally and photo-initiated thiol-ene/thiol-yne and Diels-Alder reactions, have been used for surface functionalization of PU foams. As a result of diffusional effects, the reaction rate was considerably depressed and thus, the reaction parameters, including the temperature and the concentration of reagents and the "click" compound, were optimized for each click/coupling approach to obtain high functionalization yields. As such, a kinetic comparison study of the different chemistries used was performed, using in situ FT-IR and offline H-1 NMR methods. This work not only reveals kinetic trends but also compares promising and limiting aspects of the different click/coupling pathways employed, which is envisaged to be also useful for functionalizing other cross-linked polymeric materials.

The production of poly(butylene terephthalate) (PBT) struggles with the formation of substantial amounts of tetrahydrofuran (THF). When PBT is synthesized from terephthalic acid (TPA) instead of dimethyl terephthalate (DMT), even more THF is formed, mainly during the first stage of the melt polymerization process. Although a lot of literature reports on the existence of this side reaction in both processes, to the best of our knowledge, a comparison, which reveals the importance of the acidity and insolubility of TPA on the THF formation, was never described. Finally, an interesting study was performed on the THF formation during the synthesis of PBT from mixtures of DMT and TPA as well as from the completely soluble monomethyl terephthalate (MMT). (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 2427-2434, 2009

An in depth study is performed on the origin of and influences on the formation of tetrahydrofuran (THF) during the first stage of the terephthalic acid (TPA) based synthesis of poly(butylene terephthalate) (PBT). Although many improvements on the synthesis process of PBT have been reported in literature to suppress this undesired side reaction, only few studies reported on the actual mechanism of the THF formation, which is not completely understood. Low molecular weight compounds have been used to model the side reactions occurring during the polymerization reaction. It could be concluded that, in contrast to previous reportage, only the THF formation from the monomer, 1,4-butanediol, is directly influenced by the use of TPA as a starting material for the production of PBT. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 2435-2444, 2009

Copolyamides, based on 1,12-dodecanedicarboxylic acid and different ratios of 1,2-ethylenediamine and piperazine, i.e., PA-(2.14-co-pip.14), as well as the corresponding homopolymers PA-2.14 and PA-pip.14, were studied by SAXS and WAXS. Up to a pip mole ratio of 0.62, the 2.14 and pip.14 units cocrystallize in a common crystal lattice, slightly deviating from the structure of homopolyamide 2.14. The hydrogen bonds obviously tolerate significant amounts of comonomer before the crystal structure is changed significantly. For pip mole percentages of 0.90 and higher, both repeating units cocrystallize in a slightly distorted PA-pip.14 crystal structure. For pip mole percentages of 0.70 and 0.82, however, the X-ray patterns show peaks that stem from both the PA-2.14- and the PA-pip.14-like crystalline structure, indicating that the two structures coexist in this composition range. Since the intersheet distance practically remains unaffected upon incorporation of the piperazine rings, it is concluded that these rings are oriented parallel to the hydrogen-bonded sheets. Furthermore, from the composition dependency of the experimentally determined lattice spacings, keeping in mind that the intersheet distance is constant, it is concluded that the hydrogen-bonded sheets are shifted parallel to one another.

Copolyamides 2.14/piperazine.14 with variable built-in ratios of 1,2-ethyl-enediamine (1,2-EDA) and piperazine (pip) were synthesized by solution polycondensation. The built-in ratio of both diamine comonomers was determined with solution C-13 NMR analysis. The gradual replacement of 1,2-EDA units by cycloaliphatic pip units in polyamide 2.14 resulted in a progressively decreased melting (T.) and crystallization temperature of the obtained copolyamides. Apparently, the T-m raising effect of the incorporation of rigid cycloaliphatic moieties is overruled by the simultaneous T. reduction caused by a decreasing hydrogen-bond density. Indications for cocrystallization of 2.14 and pip.14 repeating units were obtained by the thermal analysis of copolyamides 2.14/pip.14 and of a blend of both homopolyamides. A preliminary wide-angle X-ray diffraction study pointed to the same conclusion. Solid-state NMR spectroscopy was used to investigate the influence of the composition on the percentage of the rigid phase of the copolyamides and delivered additional indications for cocrystallization. (C) 2003 Wiley Periodicals, Inc.