Preparation of novel antibacterial and cytocompatible polyurethane membranes as occlusive dressing, which can provide moist and sterile environment over mild exudative wounds is considered in this work. In this regard, an epoxy-terminated polyurethane (EPU) prepolymer based on castor oil and glycidyltriethylammonium chloride (GTEAC) as a reactive bactericidal agent were synthesized. Polyurethane membranes were prepared through cocuring of EPU and different content of GTEAC with 1,4-butane diamine. The physical and mechanical properties, as well as cytocompatibility and antibacterial performance of prepared membranes were studied. Depending on their chemical formulations, the equilibrium water absorption and water vapor transmission rate values of the membranes were in ranges of 3–85% and 53–154g m−2 day−1, respectively. Therefore, these transparent membranes can maintain for a long period the moist environment over the wounds with low exudates. Detailed cytotoxicity analysis of samples against mouse L929 fibroblast and MCA-3D keratinocyte cells showed good level of cytocompatibility of membranes after purification via extraction of residual unreacted GTEAC moieties. The antibacterial activity of the membranes against Escherichia coli and Staphylococcus aureus bacteria was also studied. The membrane containing 50% GTEAC exhibited an effective antibacterial activity, while showed acceptable cytocompatibility and therefore, can be applied as an antibacterial occlusive wound dressing. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 84–96, 2014.

Preparation and characterization of novel antibacterial castor oil-based polyurethane membranes for wound dressing application.

Great interest has been shown in the kinetics and mechanisms of free radical copolymerizations that produce highly alternating copolymers. In many of these systems the production of alternating copolymers seems to arise naturally, while in others it is necessary to add a metal halide or an organometal halide regulating agent to modify reactivities. Much of the interest in alternating radical copolymerizations centers around the precise mechanism of alternation and in particular whether or not any of the alternation arises from the involvement of monomer-monomer donor-acceptor complexes (sometimes called charge-transfer complexes).

On the role of monomer-monomer complexes in alternating free-radical copolymerizations: the case of styrene and maleic anhydride

This article surveys methods and mechanisms of synthesis and characterization of hydroxytelechelic polymers by the free radical process. Some practical applications have been considered.

Hydroxyl-terminated polymers obtained by free radical polymerization — Synthesis, characterization, and applications

Alternating Addition Copolymerizations

Polymers are produced on an enormous scale globally and the majority of plastic waste is either incinerated - generating toxic substances - or placed in landfill sites where it can take many decades to decompose. It is estimated that 22% of the total volume of all landfill sites are occupied by waste plastics. In the United Kingdom over 100kg per person of plastic packaging waste is generated each year; this offers a potential stream of raw material that is currently not reused or recycled. 
In this work the synthesis of lubricant additives from waste commodity polymers is described. A degradation method using an adapted microwave reactor and selected reagents allows for the degradation of commodity polymers; polystyrene and polyethylene into terminal double bond olefin oligomers. A variety of Novel block copolymer dispersant viscosity modifiers were synthesised from polystyrene, maleic anhydride, stearyl methacrylate and various N-maleimides using Reversible Addition Chain Transfer-fragmentation (RAFT) Polymerisation. Degraded polystyrene was incorporated into the synthesis of the novel dispersant viscosity modifiers. An analytical method involving offline and online 1H and 13C NMR and FTIR spectroscopy was used to characterise the degraded polystyrene and its incorporation into the dispersant viscosity modifier along with GPC, GC-MS and MALDI-MS. The reaction kinetics at the beginning of the RAFT polymerisation of styrene and maleic anhydride was also studied and lead to the development of a method to control the placement of alternating blocks of styrene-alt-maleic anhydride within a polymer backbone, offering the potential to afford complex macromolecular architectures in one pot synthesis reactions. Finally, the novel dispersants and other potential lubricant additive synthesis products were subjected to viscometric, rheological and thermal testing by formulation into a Heavy Duty engine oil formulation.

Gregory J. Hunt, Durham 2010

The synthesis of lubricant additives from waste commodity polymers

The kinetics of copolymerization of styrene and maleic anhydride in acetic anhydride has been investigated by the dilatometric method. It was found that the order of reaction with respect to the product of the monomer concentrations is close to 0·5 and the reaction rate increases as the proportion of maleic anhydride is increased. This indicates the occurrence of alternating copolymerization by successive addition of the monomers. The kinetic parameters of the system were determined.

The kinetics and mechanism of alternating copolymerization of styrene with maleic anhydride

Oligomerization of isoprene on initiation by hydrogen peroxide in solutions of methyl, ethyl, propyl and carbon-labelled isopropyl alcohols is studied. The radioactive label method reveals that the functionality of the oligomers for fragments of isopropyl alcohol is about 0·5 irrespective of the molecular weight of the oligomers and degree of monomer conversion. The presence of fragments of isopropyl alcohol with the terminal tertiary OH groups in the oligomer molecule is the cause of the reduced (below 2) “effective” functionality of the oligoisoprenes obtained in solution in isopropyl alcohol. In solutions in primary alcohols oligomers containing up to 90% of molecules bifunctional in hydroxyl groups are obtained.

Study of oligomerization of isoprene on initiation with hydrogen peroxide

IR spectroscopy has been employed to study the features of the formation of the network of physical bonds in cation-containing oligoamino urethanes on their transition from the non-ionic to the ionic form. It is shown that the existing network of hydrogen bonds between the urethane groups with an energy 16 kJ/mole is completely destroyed with formation of a new network of ion-molecular hydrogen bonds between the urethane NH groups and the anion with the energy 20–23 kJ/mole with doubling of their number. The energy of the hydrogen bond is greater on formation of the salt centre by quaternization and depends little on the chemical nature of the anion and practically does not depend on it during protonization. The ion-molecular hydrogen bond in the systems studied is preferable to the dipole-dipole interaction of the ionic centres.

Study of intermolecular interactions in cation-containing oligo-urethanes with a different chemical nature of the anion

A dilatometric method was developed for determining the ratio of primary and secondary hydroxyl groups and their overall concentration in small amounts of oligomer. The method is based on the difference in reaction rates of primary and secondary hydroxyls with phenyl isocyanate in the presence of tin dibutyldilaurate. To record accurately the initial volume of the system a dilatometer with an internal valve was used. By the methods devoloped the concentration and the ratio of primary and secondary hydroxyls were determined in several oligomers. Agreement was demonstrated between the overall proportion of hydroxyls detected dilatometrically and independently by acetylation.

Dilatometric method of determining concentration of primary and secondary hydroxyls in oligomers

A study was made of polymerization kinetics of acrylonitrile (AN) in dimethylformamide, methylpyrrolidone and a dilute, saturated magnesium perchlorate solution. Kinetic constants were determined using pulse photolysis of the initiator. It was found that polymerization of AN in a dilute saturated magnesium perchlorate solution is homogeneous up to a ratio of AN to magnesium perchlorate of six. It was assumed that changes in the activity of the monomer and growing radical in reactions of chain extension and rupture are due to the co-ordination effect of solvated ions, producing a variation in activation entropy of these reactions.

T.S. Yatsimirskaya

Papers

The kinetics and mechanism of alternating copolymerization of styrene with maleic anhydride

Study of oligomerization of isoprene on initiation with hydrogen peroxide

Study of intermolecular interactions in cation-containing oligo-urethanes with a different chemical nature of the anion

Dilatometric method of determining concentration of primary and secondary hydroxyls in oligomers

Effect of the medium on polymerization of acrylonitrile