Silvia Villarroya

Epoxy functionalised poly(ε-caprolactone): synthesis and application

Glycidol is used as an initiator for ring-opening polymerisation of epsilon-caprolactone (epsilon-CL) to synthesise epoxy-functionalised poly(epsilon-caprolactone) (PCL) in a reaction catalysed by lipase, and the epoxy-functionalised PCL was further copolymerised with carbon dioxide or anhydride to produce novel graft or hyperbranched copolymers.

HRP-mediated inverse emulsion polymerisation of acrylamide in supercritical carbon dioxide

We report the horseradish peroxidase (HRP)-mediated inverse emulsion polymerisation of water-soluble acrylamide in supercritical carbon dioxide (scCO2). The enzymatic polymerisation takes place within water droplets formed in scCO2. These are either stabilised as reversed micelles using perfluoropolyether ammonium carboxylate (PFPE-COO−NH4+) or in the absence of stabiliser using very high shear. The viability of water-in-CO2 (W/C) emulsion as a reaction medium for in-situ enzyme-mediated polymerisation has been tested for the first time. There is significant interest in enzymes as they have proven to be powerful and environmentally friendly natural catalysts for the polymerisation of water-soluble monomers that can function under milder reaction conditions than those used in traditional free radical polymerisation techniques. Hence, the combination of scCO2 and water as reaction medium is a significant advancement in natural polymerisation process.

Grafting polymers by enzymatic ring opening polymerisation—maximising the grafting efficiency

The synthesis of well-defined graft copolymers containing alkyl methacrylate, hydroxylalkyl methacrylate monomers and/or (poly(ethylene oxide) methacrylate macromonomers and their further graft chain extension with poly(e-caprolactone) (PCL) was studied in both conventional solvents and supercritical carbon dioxide (scCO2). A cascade two-step synthetic approach was adopted in which copolymer backbones were prepared in a first stage via atom transfer radical polymerisation (ATRP). These copolymers take the form of methacrylate based polymer backbones. In one case hydroxyl groups are pendant and close to the backbone (poly(MMA-co-HEMA)) whilst in the second, the hydroxyl groups are present as the terminal group of a poly(ethylene oxide) graft arm significantly separated from the main backbone (poly(MMA-co-PEGMA)). In stage two, these hydroxyl moieties were then used as the initiation centre for further chain extension via enzymatic ring opening polymerisation (eROP). These studies were designed to prepare different poly(alkyl methacrylate) copolymers by ATRP to optimise the grafting efficiency of the enzymatic polymerisation. We previously reported a limited grafting level of up to 40% for the pendant hydroxyl groups of a poly(MMA-co-HEMA) copolymer system. This study demonstrated that higher grafting efficiency (up to 80%) could be obtained by using a highly randomized MMA-co-HEMA polymeric backbone. By contrast, 100% grafting was achieved by moving the hydroxyl groups away from the backbone when using the longer hydroxyl-terminated poly(ethylene oxide) methacrylate monomer (PEGMA) as a co-monomer in poly(MMA-co-PEGMA) backbones.

Supercritical CO2: an effective medium for the chemo-enzymatic synthesis of block copolymers?

In this review, we describe the combination of enzymatic polymerisation and controlled free radical polymerisation in supercritical carbon dioxide. This combination facilitates the preparation of a range of block and graft copolymers, some of which cannot easily be obtained by conventional polymer synthesis. Biocatalysis in polymer science provides significant new opportunities and will open up a very broad range of new polymeric materials.