Showing papers by "Harry R. Allcock published in 2013"
TL;DR: In this paper, a supramolecular-structured hydrogel system based on the inclusion complex between the mPEG grafted polyphosphazenes and α-cyclodextrin was prepared in aqueous media.
Abstract: Biodegradable poly(organophosphazenes) containing side chains of various oligo(ethylene glycol) methyl ethers (mPEGs) and glycine ethyl ester units were synthesized and characterized. Novel supramolecular-structured hydrogel systems based on the inclusion complex between the mPEG grafted polyphosphazenes and α-cyclodextrin were prepared in aqueous media. The gelation time depended on the length of the mPEG side chains, the molar ratio between mPEG repeat units and α-cyclodextrin, and the concentration of the polymeric gel precursors. The rheological measurements of the supramolecular hydrogels indicate a fast gelation process and flowable character under a large strain. The hydrogel systems demonstrate unique structure-related reversible gel–sol transition properties at a certain temperature due to the reversible supramolecular assembly. The formation of a channel-type inclusion complex induced gelation mechanism was studied by DSC, TGA, 13C CP/MAS NMR, and X-ray diffraction techniques. The strong potenti...
67 citations
TL;DR: In this paper, the carboxylic acid moiety of the amino acids L-alanine and L-phenylalanine were protected with alkyl esters with increasing chain length from 5 to 8 carbon atoms.
44 citations
TL;DR: Various amino acid ethyl esters were linked to the polymers as co-substituents to increase the solubility as well as to control the rate of antibiotic release to prevent cross-linking of multi-functional reagents with polymers.
42 citations
TL;DR: Polyphosphazenes are macromolecules with a chain of alternating phosphorus and nitrogen atoms and with two (usually) organic side groups linked to each phosphorus as discussed by the authors, with a wide variety of different properties.
Abstract: Polyphosphazenes are macromolecules with a chain of alternating phosphorus and nitrogen atoms and with two (usually) organic side groups linked to each phosphorus. Although the earliest poly(organophosphazenes) were essentially linear polymers each bearing only one type of side group along the chain, research in our program in recent years has widened the scope to include mixed-substituent polymers with two or more different side groups, block copolymers, comb structures, stars, and dendrimers, all with a wide variety of different properties. In addition, supramolecular systems have also been synthesized including vesicles, microspheres, and a variety of composite systems. This review provides a summary of these developments together with an introduction to the widening array of developing uses. Copyright © 2013 John Wiley & Sons, Ltd.
38 citations
TL;DR: In this paper, a 6-arm amphiphilic block copolymer and a UV-cleavable core with photolabile o-nitrobenzyl groups have been synthesized and characterized.
30 citations
TL;DR: The results show that the viscosity, glass transition temperatures, and conductivity of the phosphates are dependent mainly on the length of the longest alkyleneoxy chain.
Abstract: A homologous series of fire-retardant oligoalkyleneoxy- phosphates was synthesized for evaluation as liquid or gel-type electrolyte media for dye-sensitized solar cells (DSSCs) and secondary lithium batteries. Unoptimized DSSC electrolyte formulations for DSSCs achieved ionic conductivities as high as 5.71 × 10 �3 S·cm �1 and DSSC test-cell efficiencies up to 3.6% as well as Voc, Jsc, and ff up to 0.81 V, 8.03 mA·cm �2 , and 0.69, respectively. Poly(bis-(2-(2-methoxyethoxy)ethoxy)phosphazene)-based Li + -conducting gel electrolytes plasticized with the best performing phosphate had conductivities as high as 9.9 × 10 �4 S·cm �1 at 30 °C. All the liquids have boiling points higher than 197 °C. The results show that the viscosity, glass transition temperatures, and conductivity of the phosphates are dependent mainly on the length of the longest alkyleneoxy chain.
14 citations
TL;DR: In this paper, a biodegradable alanine-substituted polyphosphazene nanofibrous scaffold was prepared by an electrospinning technique.
13 citations
TL;DR: In this paper, the synthesis and characterization of novel poly (CTFE-g-oligoEO) graft copolymers (chlorotrifluoroethylene and ethylene oxide) are presented.
Abstract: The synthesis and characterization of novel poly (CTFE-g-oligoEO) graft copolymers (chlorotrifluoroethylene (CTFE) and ethylene oxide (EO)) are presented. First, vinyl ether monomers bearing oligo(EO) were prepared by transe- therification of x-hydroxyoligo(EO) with ethyl vinyl ether catalyzed by a palladium complex in 70-84% yields. Two vinyl ethers of different molecular weights (three and 10 EO units) were thus obtained. Then, radical copolymerization of the above vinyl ethers with CTFE led to alternating poly(CTFE-alt- VE) copolymers that bore oligo(OE) side chains in satisfactory yields (65%). These original poly(CTFE-g-oligoEO) graft copolymers were characterized by 1 H, 19 F, and 13 C NMR spec- troscopy. Their molecular weights reached 19,000 g mol � 1 , and their thermal properties were investigated while their
12 citations
TL;DR: Mossbauer and Eiseman as mentioned in this paper showed that cyclotriphosphazene substituted with an iron(II)-bis-2,6-di(1H-pyrazoly-yl)pyridine moiety and its polyphosphzene analogue differ significantly in magnetic behaviour.
6 citations
TL;DR: In this paper, surface morphology and wetting behavior of one aryl and three fluorous polyphosphazenes are described, and the resulting structure property relationships define trends in processability, hydrophobicity and oleophobicity.
6 citations