Polyaryl ethers and related polysiloxane copolymer molecular coatings preparation and radiation degrdation

Poly(arylene ether sulfones) comprise a class of materials known as engineering thermoplastics which have a variety of important applications. These polymers are tough, rigid materials with good mechanical properties over a wide temperature range, and they are processed by conventional methods into products typically having excellent hydrolytic, thermal, oxidative and dimensional stability. Wholly aromatic random copolymers of hydroquinone and biphenol with 4.4 prime dichlorodiphenyl sulfone were synthesized via mechanical nucleophilic displacement. Their structures were characterized and mechanical behavior studied. These tough, ductile copolymers show excellent radiation resistance to electron beam treatment and retain much of the mechanical properties up to at least 700 Mrads under argon

Use and efficacy of bone morphogenetic proteins in fracture healing

Signal transduction in aging related disease

Electrospinning of polyurethane fibers

A segmented polyurethaneurea based on poly (tetramethylene oxide)glycol, a cycloaliphatic diisocyanate and an unsymmetrical diamine were prepared. Urea content of the copolymer was 35 wt%. Electrospinning behavior of this elastomeric polyurethaneurea copolymer in solution was studied. The effects of electrical field, temperature, conductivity and viscosity of the solution on the electrospinning process and morphology and property of the fibers obtained were investigated. Results of observations made by optical microscope, atomic force microscope and scanning electron microscope were interpreted and compared with literature data available on the electrospinning behavior of other polymeric systems

Real time mechano-optical study on deformation behavior of PTMO/CHDI-based polyetherurethanes under uniaxial extension

Real time mechano-optical properties of two homologous segmented, thermoplastic polyurethanes (TPUs) obtained from the stoichiometric reactions of trans-1,4-cyclohexyl diisocyanate (CHDI) and poly(tetramethylene oxide)glycol (PTMO) were investigated. PTMO oligomers used had number average molecular weights 〈Mn〉 of 1020 and 2040g/mol, resulting in TPUs with urethane hard segment contents of 14 and 7.5% by weight. AFM studies showed intertwined microphase morphology. Stress–strain measurements demonstrated the formation of very strong, elastomeric materials, with ultimate tensile strengths of 23–25MPa and elongation at break values of about 1000%. Mechano-optical behavior of these polymers exhibited multiple regime behavior. The first strain optical regime is linear where primarily the soft segments orient. The transition between the first and second strain optical regimes was found to correspond to the saturation of straining of the soft segments that lead to start of rotation of hard segments in the stretching direction. The start of Regime II coincides with the onset of strain hardening and the distance between the hard segments increases appreciably with stretching in this regime. Increasing the soft segment length was found to promote its strain-induced crystallization

Effect of intersegmental interactions on the morphology of segmented polyurethanes with mixed soft segments: A coarse-grained simulation study

Segmented thermoplastic polyurethanes, polyureas and polyurethaneureas (TPU) based on a given hard segment and two chemically different soft segments display interesting microphase morphologies and thermal, mechanical and surface properties. In these systems the final TPU morphology is mainly controlled by the structure, amount and molecular weight of the soft segment oligomers and the nature and extent of specific intermolecular interactions between the mixed soft segments themselves and with the urethane hard segments. These interactions lead to variable compatibilities between the soft and hard segments resulting in interesting TPU morphologies. The proper choice of the two chemically different soft blocks provides more flexibility in controlling the extent of microphase separation, size and shape of the microphase domains and offers new possibilities for controlling the properties of TPUs. In this study coarse grained computer simulations were carried out to better understand the nature of intermolecular interactions and to elucidate the equilibrium microphase morphologies of TPUs with two different soft segments at 300 K. Model TPU systems investigated are comprised of poly(tetramethylene oxide) (PTMO) or poly(hexylethyl carbonate) (PHEC) and polydimethylsiloxane (PDMS) or polyisobutylene (PIB) soft segments with molecular weights in the range of 500-2500 g/mol. Hard segments consisted, in all cases, of diphenylmethane diisocyanate (MDI) based urethane repeat units and ranged from 25 to 50% by weight. Through coarse grained Dissipative Particle Dynamics (DPD) simulations it was demonstrated that by varying the composition and the chain lengths of the soft and hard blocks, quite different morphologies from homogeneous (or mixed) to gradient and to completely microphase separated structures were attainable. As expected, fairly hydrophobic soft blocks such as PIB and PDMS favored strong microphase separation when compared with relatively hydrophilic PHEC and PTMO segments. For comparison, morphologies of the TPUs based on single soft segments (PTMO, PHEC, PDMS and PEO) with varying molecular weights and hard segment contents were also simulated

Proliferation and differentiation of mesenchymal stem cells in chitosan scaffolds loaded with nanocapsules containing bone morphogenetic proteins-4, Platelet-derived growth factor and insulin-like growth factor 1

Periodontal regeneration is a complex healing pattern of soft and hard periodontal tissues. Recent approaches in reconstructive biology utilize mechanical, cellular or biologic mediators to facilitate reconstruction/regeneration of a particular tissue. In this study, the concept of tissue engineering was applied by using biodegradable chitosan scaffolds containing nanocapsules having different degradation rates and loaded with various growth factors (GFs). For this purpose, nanocapsules of faster degrading poly(lacticacid-co-glycolic acid) (PLGA) and slower degrading poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) were separately loaded with bone morphogenetic protein 4 (BMP-4), platelet-derived growth factor (PDGF) and Insulin-like growth factor 1 (IGF-I) and nanocapsules were incorporated into chitosan scaffolds. PLGA capsules had a particle size in the range of 190–615 nm with an average diameter of 327 nm where PHBV capsules were found to have particle size in the range of 255–712 nm with a larger mean diameter of 438 nm. The morphology of chitosan scaffolds showed a sponge-like open porous microstructure with pore size around 100-200 µm. Human mesenchymal stem cells were used in in vitro studies. It was observed that simultaneous fast delivery of BMP-4 and PDGF led to highest proliferation rate. All cell seeded scaffolds were positive for mineralization which was determined by von Kossa staining. © 2014 American Scientific Publishers. All rights reserved