Carl Braybrook

Topochemical photo-reversible polymerization of a bioinspired monomer and its recovery and repolymerization after photo-depolymerization

Solid-state topochemical polymerization is one way to synthesize novel macromolecular architectures with stereoregular chain structures. Topochemical reactions are attractive, “green” synthetic pathways in material design, since they occur in solvent-free conditions and in response to external stimuli, such as heat and light. For the first time, we have used the reversible [2π + 2π]-cycloaddition of a bioinspired bis-thymine monomer to topochemically synthesize a polymer. The polymer can be fully photo-depolymerized to the monomer and then reversibly and repeatedly photo-polymerized and photo-depolymerized. This is the first demonstration of complete photo-depolymerization and subsequent monomer recycling using this mechanism.

Biocompatibility and modification of the protein‐based adhesive secreted by the Australian frog Notaden bennetti

When provoked, Notaden bennetti frogs secrete a proteinaceous exudate, which rapidly forms a tacky and elastic glue. This material has potential in biomedical applications. Cultured cells attached and proliferated well on glue-coated tissue culture polystyrene, but migrated somewhat slower than on uncoated surfaces. In organ culture, dissolved glue successfully adhered collagen-coated perfluoropolyether lenses to debrided bovine corneas and supported epithelial regrowth. Small pellets of glue implanted subcutaneously into mice were resorbed by surrounding tissues, and all of the animals made a full recovery. An initial but transient skin necrosis at the implant site was probably caused by some of the potentially toxic metabolites present in the frog secretion; these include sterols and carotenoids, as well as fatty alcohols, aldehydes, ketones, acids, and aromatic compounds. Removal of the carotenoid pigments did not significantly alter the glues material properties. In contrast, peroxidase treatment of dissolved glue introduced unnatural crosslinks between molecules of the major protein (Nb-1R) and resulted in the formation of a soft hydrogel, which was very different to the original material.

Synthesis of Acyclic, Symmetrical 3,3′-Allyl Dithioethers, from the Alkylation of 3-Mercapto-2-mercaptomethylprop-1-ene in the Presence of Sodium Hydride

A novel method where 3,3′-allyl dithioethers have been prepared from 3-mercapto-2-mercaptomethylprop-1-ene and two mol equivalent of alkyl halide in the presence of two mol equivalent of sodium hydride has been developed. Using this method, bisepoxide, 2,2′-(2-methylenepropane-1,3-diyl)bis(sulfanediyl)bis(methylene)dioxirane (8) has been synthesized from epichlorohydrin, whereas potassium carbonate was unable to deliver this product. These 3,3′-allyl dithioethers can be utilized either as monomers, or with further chemical reactions transformed into more complex monomers, for photoplastic polymer networks.

Synthesis of Symmetrical, Substituted (alkane-α,ω-diyl)(bis[3,3′-allyl dithioethers]) Monomers for Photoplastic Polymer Networks

Novel symmetrical (alkane-α,ω-diyl)(bis[3,3′-allyl dithioethers]) compounds and their ether analogues, have been synthesised from (alkane-α,ω-diyl)bis([2-{chloromethyl}allyl]sulfane) precursors, for use in crosslinked polymers which exhibit photoplastic behaviour. Facile synthesis and purification of these monomers was achieved if the alkane-α,ω-diyl moiety had at least one oxygen atom in this linker. The number of sulfur atoms in these monomers was varied from four to two to zero to produce monomers which can be used to evaluate their importance on the photoplasticity behaviour.

A Unique Toxic Peptide from the Larvae of the South American Sawfly, Perreyia flavipes.

A major toxic component of the South American sawfly larvae, Perreyia flavipes (Pergidae), has been shown to be a heptapeptide with the structure (1). The unique features of this peptide, which has been named pergidin, are the presence of five unnatural D amino acids and a phosphoseryl residue.

Topochemical polymerization using bis-thyminyl monomers

Topochemical polymerization is one way to synthesize novel macromolecular architectures with stereoregular chain structures. The [2π + 2π]-cycloaddition of certain conjugated diolefin monomers is one such form of topochemical polymerization. Unfortunately, the design of new monomers that can undergo topochemical [2π + 2π]-polymerization to form linear polymers can be a formidable challenge due to the strict geometrical criteria governing the reactivity of monomer crystals. In this research ten bis-thymine monomers were synthesized, that varied with respect to the N1-functionality, the size of the N3–N3-polymethylene spacer, or the type of rigid N3–N3-aryl spacer employed. On irradiation, five of the crystalline monomers were found to undergo topochemical photo-reactions. The crystal structures of the bis-thyminyl monomers were used to investigate the monomer structure–reactivity relationships. The molecular weights of the photo-products were determined and the thermal properties of some of the new materials were also evaluated using thermo analytical techniques.

Preparation of liquid substituted benzoyl peroxide mixtures

A series of alkyl substituted benzoyl peroxide mixtures were synthesised from two or three acid chloride combinations in aqueous sodium peroxide and butanone solutions to form liquid benzoyl peroxide mixtures.