Aliphatic polyalkenes

Pincer-ligated iridium complexes have been used as homogeneous catalysts for the dehydrogenation of aliphatic polyalkenes to give partially unsaturated polymers. The catalyst appears to be selective for dehydrogenation in branches as compared with the backbone of the polymer.56 The mechanism shown in Scheme 1 has been suggested for an [IrCl(cod)]2-catalysed oxidative esterification reaction of aliphatic aldehydes and olefinic alcohols.57... 

Although PET and PBT are widely used, better thermal and mechanical properties are desired for some applications. Higher performance in semiaromatic polyesters was obtained from polyalkene naph-thalates. These semicrystalline polyesters are prepared by the condensation polymerization of naphtha-lene-2,6-dicarboxylic acid and flexible aliphatic diols. The naphthalene moiety imparts stiffness to the linear polymer backbone, leading to improved physical and mechanical, barrier, chemical resistance properties, and UV-ray screening performance. Poly(ethylene naphthalene-2,6-dicarboxylate), PEN, became commercially available from Teijin Ltd. in the early 1970s. PEN has a Tg and of 125 and 268°C, respectively [34]. Its structure appears in Fig. 1.18. 

Section 14.6) and hence the attempts to overcome the network constraints in nylon 6,6 fibres cannot be rated as successful the same applies to nylon 6 and PET. In contrast, the superdrawing of melt-spun polyethylene and polypropylene fibres is well established. In the case of polyethylene it was possible, by optimization of polymer molecular weight and spinning as well as drawing conditions, to obtain a fibre with a tenacity of 1.75Ntex and extension at break of 3.9% i.e sg over 1.8 N tex It appears that, due to weaker intermolecular interactions in polyalkenes compared with aliphatic polyamides and PET, it is much easier to overcome the network constraints. 

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