Synthesizing lignin-based copolymers would valorize a major coproduct stream from pulp and paper mills and biorefineries as well as reduce the dependence on petrochemical-based consumer goods. In this study, we used organosolv lignin isolated from hybrid poplar ( Populus trichocarpa × P. deltoides) to generate lignin-containing methacrylate hydrogels. The copolymer hydrogels were synthesized by first grafting 2-hydroxyethyl methacrylate (HEMA) onto lignin (OSLH) via esterification and then by free radical polymerization of OSLH with excess HEMA. The copolymer hydrogels were prepared with different stoichiometric ratios of OSLH (e.g., 0, 10, 20, and 40 wt %) with respect to HEMA. Copolymerization with OSLH led to an increase in cross-linking density, which in turn enhanced the hydrogel's material properties; we report up to 39% improvement in water retention, 20% increase in thermostability, and up to a 3 order increase in magnitude of the storage modulus ( G'). The copolymer's properties, such as water retention and glass transition temperature, could be tuned by altering the percent functionalization of lignin OH groups and the ratio of OSLH to HEMA.

Three recent attempts to formulate a reaction mechanism for scission during the oxidation of rubber have been evaluated with respect to their predictions concerning the formation of formic acid and the step at which scission occurs. Two do not account directly for formic acid as a principal product or for the failure of antioxidants to influence scission yield. The third, while consistent with available evidence, does not predict the observed product distribution as a necessary consequence of decomposition of the postulated intermediate.

synopsisAcetic and formic acids and acetone are products of the oxidation of propylene and ethylene polymers and copolymers. The two-and three-carbon products can be accounted for as the result of intramolecular attack by radicals, leading to &oxidation. A high proportion of scissions in polypropylene involves multiple intmmolecular attack.This papcr reports some observations pcrtincnt to the mechanism of oxidation of polyethylene and polypropylene. A number of previous investigations have dealt with other aspects of the oxidation process, including effects of temperature, crystallinit~y, and other external conditions. '-I8

Rhodospirillum rubnim cell suspensions, disrupted by sonication, yield chromatophores which can be depleted by washing to give minimal photophosphorylation and dark-phosphorylation rates. Photophosphorylation by such chromatophores can be restored to a maximal rate by an optimal concentration of ascorbate (4.7 X 10-8 m) added externally. The same maximal rate is obtained by addition of phenazine methosulfate or by addition of endogenous co-factors, either lumped together in a "supernatant fraction" (chromatophore washings) or as single purified components (flavins, heme proteins). Further, the amounts of chromatophore washings which produce the characteristic maximal rate of photophosphorylation have reducing power equivalent to ascorbate at a concentration of 2.2 X 10~8 m. Cytochrome c2 and riboflavin exhibit special effects which show that the former has substrate specificity as a terminal acceptor in the electron-transport system which supports photophosphorylation, while the latter is apparently active at the photophosphorylation site as the co-factor for a pyridine nucleotide-linked flavoenzyme heme protein reductase. All of the results found are in accord with the suggestion that a circular chain of respiratory catalysts is present which is coupled to phosphorylation optimally at an effective intrachromatophore oxidationreduction potential of ~0.0 ± 0.01 volts.

synopsisProducts of the oxidation of cis-polyisoprene boiling lower than water have been resolved and identified. They are: acetaldehyde, methyl formate, propionaldehyde, acetone, methanol, sylvan, methacrolein, ethanol, butanone, and butenone. Possible mechanisms for their origin are discussed.