Allan J. Amass

A review of biodegradable polymers: uses, current developments in the synthesis and characterization of biodegradable polyesters, blends of biodegradable polymers and recent advances in biodegradation studies

This review considers the uses of biodegradable polymers in terms of their relevance within current plastic waste management of packaging materials, biomedical applications and other uses; research papers and patents are catalogued. The chemical synthesis of polyesters and the microbial production of poly(hydroxyalkanoate)s, including recent publications in these areas, are covered and methods of characterization and structural analysis are outlined. Current research into two- and three-component blends is reviewed as a method of reducing overall costs and modifying both properties and biodegradation rates of materials. Finally, there is a summary of degradation processes. Both abiotic and biotic reactions are discussed, together with the development of biodegradation test methods, particularly with respect to composting.

Synthesis of narrow molecular weight α,ω-hydroxy telechelic poly(glycidyl nitrate) and estimation of theoretical heat of explosion

Abstract This communication reports the synthetic steps and characterization required to make pure poly(glycidyl nitrate), also known as polyGLYN or POWA3, from cheap commercially available starting materials using dinitrogen pentoxide (N 2 O 5 ) technology. Conditions are given whereby a range of well defined and characterized polyGLYN samples may be safely and reproducibly prepared by the cationic, ring-opening, activated monomer mechanism (AMM). Tetrafluoroboric acid and 1,4-butanediol were used as the catalyst system, and the samples have been characterized by nuclear magnetic resonance spectroscopy, size exclusion chromatography, infra-red spectroscopy and differential scanning calorimetry. The theoretical calculations indicate that the heat of explosion is 2661 kJ kg −1 , this being significantly more energy than for earlier polymers. These materials are currently under assessment in both high-performance explosives and high-energy low-vulnerability propellant systems. Some properties of the material are also shown.

Synthesis and characterization of α,ω-hydroxy and nitrato telechelic oligomers of 3,3-(nitratomethyl) methyl oxetane (NIMMO) and glycidyl nitrate (GLYN)

Abstract The synthesis of α,ω-hydroxy telechelic, low-molecular-weight oligomers (degree of polymerization of less than 10) of glycidyl nitrate (GLYN) and 3,3-(nitratomethyl) methyl oxetane (NIMMO) by the activated monomer mechanism is described. Difunctional and/or trifunctional compounds may be prepared. The end-nitration of these compounds has been investigated using dinitrogen pentoxide in dichloromethane to form α,ω-nitrato telechelic oligomers. The materials were characterized by size exclusion chromatography, infrared and nuclear magnetic resonance spectroscopies. Differential scanning calorimetry was used to study the thermal properties of the compounds as they are envisaged to be energetic and fully compatible (miscible) plasticizers for the new generation of energetic binders such as polyNIMMO or polyGLYN, in propellant and explosive applications.

Synthesis of block and graft copolymers containing polyacetylene segments

Abstract The area of conducting polymers has been the subject of a great deal of discussion in the literature over the last 15 years. Polyacetylene is the material that has received the most attention during this period with strenuous efforts being made to produce a soluble copolymer containing polyacetylene segments. This paper is an overview of the synthetic techniques that have been used in order to try and produce these materials, which are both highly conducting and soluble in common organic solvents. Special emphasis has been placed upon the work which has led to the development of new catalyst systems and the work that has combined previously well characterized catalyst systems to produce novel materials.

N-alkyl-2-pyridinemethanimine mediated atom transfer radical polymerisation of styrene : the transition from heterogeneous to homogeneous catalysis

The polymerisation of styrene was studied using Cu(I)/Cu(II)-based atom transfer radical polymerisation catalysts in conjunction with a variety of N-alkyl-2-pyridinemethanimines as complex ligands. Increasing the length of alkyl chain on the ligand from propyl to octyl resulted in a catalyst complex with improved solubility in xylene, and enabled the production of polymers of narrower molecular weight distribution. The molecular weight distribution was further narrowed by changing the solvent to a more polar system, diglyme, in which case polymers with (Mw/Mn)=1.1–1.2 were produced, and the catalyst system generated shows possibility of being amenable to kinetic study. The narrow molecular weight distribution is consistent with a soluble catalyst promoting rapid exchange of a halogenated chain end into an active form.

Synthesis of narrow molecular weight distribution α,ω-hydroxy telechelic polyoxetane by the activated monomer mechanism

Abstract The cationic activated monomer mechanism has been used to prepare polyoxetane (poly(trimethylene oxide)) with low dispersities, hydroxy functional end groups and without significant oligomer contamination. Tetrafluoroboric acid and 1,4-butandiol were used as the catalyst system. The polymer has been characterized by n.m.r. and s.e.c.

The kinetics of polymerization of cyclopentene by WCl6/AliBu3 catalyst

Abstract The kinetics of the polymerization of cyclopentene by WCl 6 /AliBu 3 catalysts have been studied and the factors controlling the reproducibility of the rate of polymerization have been ascertained. A significant dependence of the rate of polymerization on the time between the additions of WCl 6 and AliBu 3 was observed. The dependence of the catalyst activity r,i this time delay suggested that WCl 6 reacted with cyclopentene to produce an unstable species (W 1 ) that could react with AliBu 3 to produce a catalytically active species (W 1 ∗ ) or that could react further with cyclopentene to produce another species W 2 that in turn would react with AliBu 3 to produce a much less active catalyst W 2 ∗ . The detailed study of the kinetics of polymerization under controlled conditions suggested a kinetic chain mechanism initiated by two catalyst species; mechanism of polymerization based on the carbene system is suggested.

Photocatalytic metathesis of 1-octene

Abstract The metathesis of 1-octene using a W(CO)6/hv/CCl4 catalyst system was studied. The conversion to 7-tetradecene depends on the initial olefin and catalyst concentrations, and on temperature. The products formed in this photocatalytic reaction were determined by GC-MS techniques. The factors which affect the product distribution were investigated. As the irradiation temperature was raised, formation of the side-products increased selectively.

Ring-opening homo- and copolymerization of lactones. Part 1. Homo- and copolymerization of racemic β-butyrolactone with ε-caprolactone and δ-valerolactone by tetraisobutyldialuminoxane (TIBAO) catalyst

Copolymers of racemic β-butyrolactone (β-BL) with e-caprolactone (e-CL) (P(BL-co-CL)) and δ-valerolactone (δ-VL) (P(BL-co-VL)) were prepared by ring-opening polymerization reactions using the commercial aluminoxane catalyst tetraisobutyldialuminoxane (TIBAO). The yields, molecular weights, compositions and crystallinities were determined for both copolymers by gel permeation chromatography (GPC), nuclear magnetic resonance (1H NMR) spectroscopy and differential scanning calorimetry (DSC). A detailed study by 13C NMR spectroscopy has been made to determine monomer diad sequence distributions. These results and those of reactivity ratios indicate that the co-polymers may consist of compatible blocks of BL units and VL units of variable size.

Studies in ring-opening polymerization—XII. The ring-opening polymerization of oxetane to living polymers using a porphinato-aluminium catalyst

Abstract The polymerization of oxetane has been carried out with catalysts derived from the reaction of 5,10,15,20-tetraphenyl-21H,23H-porphine and aluminium diethyl chloride, catalysts that have been described as immortal systems. The polymerization of oxetane with this catalyst leads to a polymerization that is slower than the corresponding polymerization of oxirane but high conversions of monomer to polymer occur and the polymerization shows the properties of a living polymerization; the molecular weight average of the polymer increases with conversion of the monomer to polymer closely correlating with the ratio of monomer polymerized to initiator used and NMR spectra show the presence of the porphinato and other end groups.