Thermal study on polyester networks based on the renewable monomers citric acid and gluconolactone

A detailed thermal study is presented of the melt polycondensation between the renewable monomers citric acid and d-glucono-δ-lactone. It was found that the polyester networks formed have glass transition temperature ranges that increase with increasing reaction temperature and time, corresponding to an increase in molecular weight. The minimum reaction temperature was investigated and found to be 130 °C for a 1/1 system. Moreover, the monomers show eutectic melt behaviour, with a eutectic melting temperature of 125 °C. A range of additional co-monomers were evaluated, revealing that aliphatic and aromatic bifunctional co-monomers result in lower glass transition temperatures. When polyfunctional co-monomers were employed it was found that the chain flexibility influenced the resulting thermal properties. Moreover, it is shown that the ring structure of d-glucono-δ-lactone plays a key role in the thermal properties of the resulting polyesters. © 2016 Society of Chemical Industr

PEGylation of surface protein filaments: coverage and impact on denaturation

N-Hydroxysuccinimidyl functional polymers for multi-site bioconjugation to amine residues present in α-keratin protein filaments were synthesised via living radical polymerisation. Monomers containing di(ethylene glycol) and poly(ethylene glycol) were employed to give water soluble polymers which were characterised using 1H NMR and size exclusion chromatography (SEC). The denaturation temperature of the PEG–keratin conjugates was examined using differential scanning calorimetry (DSC) to show that after conjugation to damaged keratinous material, the structural properties of the protein were improved against thermal degradation. Scanning electron microscopy was used to visualise surface coverage

Synthesis of water soluble PEGylated (copper) phthalocyanines via Mitsunobu reaction and Cu(i)-catalysed azide–alkyne cycloaddition (CuAAC) “click” chemistry

Octa-substituted phthalocyanine (Pc) and copper phthalocyanine (CuPc) with different chain lengths of monomethyl ether polyethylene glycol (mPEG) with molecular weights of 350, 550, 750, and up to 2000 g mol-1 were synthesised through combining a phenolic Mitsunobu reaction with Cu(i)-catalysed azide-alkyne cycloaddition (CuAAC) click chemistry. Analysis by GPC shows that narrow polydispersities (PDI ≤ 1.2) of the resultant polymeric derivatives can be achieved; photodiode array (PDA) detection confirms the formation of the desired products. The metal-free Pc polymers are clearly distinguished from polymers functionalised with CuPcs. All PEGylated (Cu)Pc polymers are highly soluble in a range of solvents and show no evidence of aggregation in common organic solvents such as chloroform, DCM, THF, etc. with a split intense Q band between 670 and 690 nm for the mPEG-Pc polymers, and a single Q band at 682 nm for the mPEG-CuPc complexes. The UV-Vis spectra of these polymers in water demonstrate that dimeric complexes are formed in all cases with a minor contribution of monomeric also found in octa-substituted mPEG-CuPc products. More remarkably, the PEGylated (Cu)Pcs with different PEG chain lengths exhibit interesting tunable thermal properties as evidenced by differential scanning calorimetry (DSC)

Biological surface modification by ‘thiol-ene’ addition of polymers synthesised by catalytic chain transfer polymerisation (CCTP)

Copolymers of oligo(ethylene glycol) methyl ether methacrylates and allyl methacrylate have been synthesised by catalytic chain transfer polymerisation (CCTP) and reacted with α-keratin in human hair via Michael addition to cysteine residues. Further modification of the polymer conjugates was carried out using a fluorescent tag as a model via achieved thiol-ene chemistry

Bioconjugation onto biological surfaces with fluorescently labeled polymers

Direct bioconjugation onto hair fibers, monitored by confocal laser scanning microscopy and differential scanning calorimetry, has been performed using NHS alpha-functional fluorescently tagged polymers synthesised by living radical polymerisation

Simple Design of an Enzyme-Inspired Supported Catalyst Based on a Catalytic Triad

Enzyme active sites afford an intricate interplay of functional groups to mediate complex organic and inorganic reactions. Many hydrolytic enzymes use a catalytic triad comprising three different functional residues—(Ser(-OH), Hist(-imidazole), Asp(-CO2H))—that catalyze the hydrolysis of numerous unique substrates. Inspired by this design, we have developed a simple one-step synthesis for preparing a new supported catalytic system in which the three reactive groups of the catalytic triad (alcohol, imidazole, and carboxylate) are incorporated into a single functional unit. These artificial active sites can be coupled to a solid-phase support (Merrifield resin) by copper(I)-catalyzed azide-alkyne cycloaddition ‘‘click chemistry,’’ and their effectiveness as esterolysis catalysts was demonstrated. Furthermore, tuning the local hydrophobicity of the resin particles with an approach analogous to the native enzyme hydrophobic pocket increased the catalytic efficiency. Quantum mechanics and molecular dynamics computational modeling were used to probe the catalytic effect and suggested a concerted two-step mechanism and hydrophobic nanoenvironment similar to that of hydrolytic enzymes.Funding from the US Army International Technology Center Pacific (ITC-PAC FA5209-14-C-0017 to L.A.C.), the Defense Science Institute (L.A.C.), a Veski Innovation Fellowship (L.A.C.), and the MRSEC Program of the National Science Foundation (award DMR-1121053 to C.J.H.) is gratefully acknowledged. M.D.N. acknowledges a John Stocker Postgraduate Fellowship, an Australian Nanotechnology Network Travel Fellowship, and an Australian Postgraduate Award. M.L.C. and M.L.O. acknowledge generous allocations of supercomputing time on the National Facility of the Australian National Computational Infrastructure and an Australian Research Council Future Fellowship. A.G. acknowledges an Endeavour Research Fellowship. Unilever and UCSB have patents covering the catalysts designed herei