Photoluminescence (PL), electroluminescence (EL) and degradation of a soluble electroluminescent poly(p-phenylene), poly[2,5-bis(isopentyloxy)-1,4-phenylene] (SPPP), and its blends with hole transport polymers based on poly[methyl(jthenyl)silandiyll (PMPSi) were studied. Efficient blue light-emitting devices (LEDs) with an air-stable (Al) electrode based on polymer blends composed of SPPP and PMPSi have been fabricated. In contrast to LEDs made of neat sPPP, an increase in external EL efficiency (up to 30 times) and improvement of the stability of blue emission were achieved in these LEDs. This enhancement is far above the increase in the PL efficiency of the blend layers. New alternately substituted poly(p-phenylene)s with high photoluminescent efficiency and new polymers with r-conjugated (pyrene, biphenyl) or electron-transporting (oxadiazole) moieties attached to the polysilane backbone were synthesized.
Two poly(amino acid) systems were studied: (a) poly[N5‐(2‐hydroxyethyl)‐L‐glutamine] (PHEG) derivatives prepared by NCA polymerization; (b) poly‐α,β‐[N‐(2‐hydroxyethyl)‐DL‐aspartamide] (PHEA) derivatives prepared by thermal polycondensation of aspartic acid to racemic polysuccinimide followed by chemical modification reactions. The degradation of polymers by isolated enzymes and homogenate of kidney tissue was studied in vitro and the effect of polymer structure on the rate of degradation and the size of degradation products was evaluated. A PHEA derivative (modified by tyramine residues in 9.6 % of side chains) was accumulated in the lysosomes of kidney cells of rats and the molecular‐weight distribution of the polymer retained inside the lysosomes of living cells and that of the polymer excreted into urine was analysed by a high‐sensitivity size‐exclusion chromatography using the fluorescence and radioactive labelling. While PHEG derivatives were degraded by isolated mammalian enzymes and a tissue homogenate, no significant degradation of PHEA and derivatives was observed, either in vitro, with isolated enzymes and homogenate or in vivo, under a long‐term exposure to the lysosomal enzymes in living cells.
The enzymatic degradation of N5-(2-hydroxyethyl)-L-glutamine homopolymer (PHEG) and its statistical copolymer with L-glutamic acid, (P[HEG-stat-Glu]) by papain, pronase and leucine aminopeptidase (LAP) was investigated with the aim to evaluate the role of endopeptidase and exopeptidase mechanisms of cleavage and to identify ultimate degradation products. The degradation products were analysed by size-exclusion chromatography, using amino end-groups labelled with fluorescamine, and by thin-layer chromatography. Papain cleaved both polymers by the endopeptidase mechanism only and the smallest degradation fragments thus produced were the size of tetramers. These fragments were susceptible to further degradation by an exopeptidase, i.e., leucine aminopeptidase. A combined treatment of polymers by papain and LAP ultimately yielded monomers, HEG only or HEG and glutamic acid for PHEG or P[HEG-stat-Glu] copolymer, respectively. Both endopeptidase and exopeptidase mechanisms were active in the degradation of the polymers under study by pronase. As the enzymes with analogous specificities are usually present in mammalian tissues, the feasibility of complete degradation of these polymers in vivo is supported.
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