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Factors affecting the syntheses of high‐molecular‐weight poly(2,5‐dialkyl‐1,4‐phenylene vinylene) by the acyclic diene metathesis polymerization of 2,5‐dialkyl‐1,4‐divinylbenzenes [alkyl = n‐octyl (2) and 2‐ethylhexyl (3)] with a molybdenum or ruthenium catalyst were explored. The polymerizations of 2 by Mo(N‐2,6‐Me2C6H3) (CHMe2 Ph)[OCMe(CF3)2]2 at 25 °C was completed with both a high initial monomer concentration and reduced pressure, affording poly(p‐phenylene vinylene)s with low polydispersity index values (number‐average molecular weight = 3.3–3.65 × 103 by gel permeation chromatography vs polystyrene standards, weight‐average molecular weight/number‐average molecular weight = 1.1–1.2), but the polymerization of 3 was not completed under the same conditions. The synthesis of structurally regular (all‐trans), defect‐free, high‐molecular‐weight 2‐ethylhexyl substituted poly(p‐phenylene vinylene)s [poly3; degree of monomer repeating unit (DPn) = ca. 16–70 by 1H NMR] with unimodal molecular weight distributions (number‐average molecular weight = 8.30–36.3 × 103 by gel permeation chromatography, weight‐average molecular weight/number‐average molecular weight = 1.6–2.1) and with defined polymer chain ends (as a vinyl group, CHCH2) was achieved when Ru(CHPh)(Cl)2(IMesH2)(PCy3) or Ru(CH‐2‐OiPr‐C6H4)(Cl)2(IMesH2) [IMesH2 = 1,3‐bis(2,4,6‐trimethylphenyl)‐2‐imidazolidinylidene] was employed as a catalyst at 50 °C. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6166–6177, 2005

Factors affecting cell viability, plating efficiency, and survival of hepatocytes after cryopreservation have been investigated. We focused especially on the effect of including trehalose and related oligosaccharides in the cryopreservation fluid. This was supplemented with either glucose, trehalose, maltotriose, or other sugars, in addition to dimethyl sulfoxide (10%) and first tested with primary rat hepatocytes cooled in a controlled rate freezer. After thawing, viability by trypan blue exclusion of cells frozen in oligosaccharide-supplemented medium was significantly higher than for those cryopreserved without oligosaccharides. Use of oligosaccharides with higher molecular weights resulted in greatest improvement in viability. Moreover, attachment and survival rates in plastic dishes were approximately 1.2-1.8-fold greater after freezing in the presence of di-, tri-, and tetrasaccharides. Human hepatocytes isolated from untransplantable liver showed the same tendency regarding viability, but cell adherence was not similarly improved by the addition of oligosaccharides. Possible reasons for these differences may be prior cell damage during extended cold ischemia of the human liver, donor age, or cell degradation caused by progression of fatty liver in humans, and/or species differences.