Rubbery wound closure adhesives. I. design, synthesis, characterization, and testing of polyisobutylene-based cyanoacrylate homo- and co-networks

Novel rubbery wound closures containing various proportions and molecular weights of polyisobutylene (PIB) and poly(2-octyl cyanoacrylate) [P(OctCA)] for potential clinical use were designed, synthesized, characterized, and tested. Homo-networks were prepared by crosslinking 3-arm star-shaped PIBs fitted with terminal cyanoacrylate groups, [Ø(PIB-CA)3], and co-networks by copolymerizing Ø(PIB-CA)3 with OctCA using N-dimethyl-p-toluidine (DMT). Neat Ø(PIB-CA)3, and Ø(PIB-CA)3/OctCA blends, upon contact with initiator, polymerize within seconds to optically transparent strong rubbery co-networks, Ø(PIB-CA)3-co-P(OctCA). Homo- and co-network formation was demonstrated by sol/gel studies, and structures and properties were characterized by a battery of techniques. The Tg of P(OctCA) is 58 °C by DSC, and 75 °C by DMTA. Co-networks comprising 25% Ø(PIB-CA)3 (Mn  = 2400 g/mol) and 75% P(OctCA) are stronger and more extensible than skin. Short and long term creep studies show co-networks exhibit high dimensional stability and \u3c6% creep strain at high loading. When deposited on porcine skin co-networks yield hermetically-adhering clear rubbery coatings. Strips of porcine skin coated with co-networks could be stretched and twisted without compromising membrane integrity. The co-network is nontoxic to L-929 mouse fibroblasts

ANIONIC SYNTHESIS OF POLY(METHYLMETHACRYLATE)-POLY(4-VINYLPYRIDINE) DIBLOCK COPOLYMERS IN THE PRESENCE OF LICL

Poly(methylmethacrylate)-poly(4-vinylpyridine) diblock copolymers were synthesized by sequential anionic polymerization. 1,1-diphenyl-3-methylpentyllithium was used as initiator and LiCl was added to the system as ligand to modify both initiator and active chain end in order to avoid side reactions. The products were characterized by H-1-NMR spectroscopy, size exclusion chromatography and differential scanning calorimetry. The block copolymers show narrow molecular weight distribution and microphase separation as indicated by the presence of two glass transition temperatures. Block copolymer formation was verified by micellization in different solvents. Also, 4-vinylpyridine block can be completely quaternized with methyl iodide as indicated by H-1-NMR and FTIR spectroscopies

A STUDY ON BLENDS OF LOW AND HIGH-DENSITY POLYETHYLENES - EFFECT OF MIXING TIME ON MECHANICAL, THERMAL-PROPERTIES AND OXIDATIVE-DEGRADATION

In this study, polyethylenes of high melt flow index LDPE and a medium melt flow index HDPE were melt blended. The mechanical, thermal properties and the thermal oxidative degradation were studied as a function of four different mixing times. The results were evaluated according to the blend composition and time of mixing. The tensile strength was found to be affected mostly by mixing time as compared with the elongation at break while the modulus remained unchanged with time of mixing. The thermal oxidative degradation of the blends were found to be less than the corresponding pure components

CONDUCTIVE PROPERTIES OF POLY(4-VINYLPYRIDINE) POLY(DIMETHYLSILOXANE) BLOCK-COPOLYMERS DOPED WITH TETRACYANOQUINODIMETHANE

Poly(4-vinylpyridine)-poly(dimethylsiloxane) (P4VP-PDMS) block copolymers with various compositions were prepared by anionic polymerization. The 4VP block was quaternized with methyl iodide and reacted with 7,7',8,8'-tetracyanoquinodimethane (TCNQ), which is in both anion radical (TCNQ-.) and neutral form (TCNQ0). The products were then characterized by H-1 nuclear magnetic resonance and Fourier-transform infra-red spectroscopy, scanning electron microscopy and differential scanning calorimetry techniques. The electrical conductivities of processable and flexible films of these block copolymers were measured with the four-probe method and found to be as high as 10(-2) S cm-1. The optimal TCNQ0 doping for which the conductivities are highest were also determined

ANIONIC SYNTHESIS AND CHARACTERIZATION OF POLY(4-VINYLPYRIDINE)-POLY(DIMETHYLSILOXANE) BLOCK COPOLYMERS

Poly(4-vinylpyridine)-b-Poly(dimethylsiloxane) (P4VP-b-PDMS) copolymers have been synthesized by sequential anionic polymerization of 4VP and hexamethylcyclotrisiloxane at - 70-degrees-C. The initiator was sodium naphthenate. The solvent used during reactions has a very critical role in an homogeneous polymerization medium. A 1:1 pyridine/THF mixture was found to be the most suitable. The products were characterized by H-1-NMR spectroscopy, transmission electron microscopy (TEM) and differential scanning calorimetry (DSC) techniques. All the results indicated the formation of 4-vinylpyridine-siloxane block copolymers. Also, the P4VP blocks can be completely quaternized with methyl iodide as indicated by H-1-NMR and FTIR spectroscopies

CONDUCTING PROPERTIES OF IODINE-DOPED POLY(4-VINYLPYRIDINE)-POLY(DIMETHYLSILOXANE) BLOCK-COPOLYMERS

Block copolymers of various compositions, consisting of poly(4-vinylpyridine) (P4VP) and poly(dimethylsiloxane) (PDMS) blocks, were prepared by anionic polymerization. These samples were modified by the addition of various amounts of iodine in solution. The electrical conductivities of the doped materials were measured by the four-probe method and were found to be as high as 10(-5) S cm(-1). The optimum ratio of iodine to pyridine which gave the highest conductivity was determined

The ionization type semiconductor photographic system based on high-resistivity polymeric cathode

A device for detecting inhomogeneities in high-resistivity poly(N-vinylimidazole) polymeric semiconductor film of large diameter (40-60 mm) is described. A measurement of homogeneity is realized by recording the spatial distribution of the gas discharge glow intensity between two parallel electrodes. The polymeric films with a resistivity of 10(6)-10(8) Omega cm (thickness 40-80 mu m) in a planar gas discharge cell, have been studied. A gas discharge gap has been formed by a dielectric separator with the thicknesses ranging from 15 to 25 mu m. A discharge has been realized in air at pressures from 60-760 Torr. The possibilities of the visualization have been evaluated, i.e. a local change of the resistance inhomogeneity is determined by a local change of discharge glow intensity the resolution of which is determined by method of its recording

Synthesis of double hydrophilic block copolymers and induced assembly with oligochitosan for the preparation of polyion complex micelles

This paper reports on the polyion complex micelles (PIC micelles) formed between neutral-ionizable double hydrophilic block copolymers (DHBC), poly(ethylene oxide)-block-poly(acrylic acid) (PEO-b-PAA), and oligochitosan, a natural polyamine. The controlled synthesis of PEO-b-PAA polymers was achieved by atom transfer radical polymerization (ATRP) of tert-butyl acrylate with omega-bromide-functionalized PEO macroinitiators (M-w = 2000 and 5000 g mol(-1)) and the subsequent deprotection reaction under acidic conditions. A series of copolymers with a narrow molecular weight distribution (M-w/M-n <= 1.2) and varied PAA block lengths was synthesized. Capillary electrophoresis (CE) was shown to unambiguously prove the blocky structure of the copolymers. It also showed that about 60% of the sodium counter ions were condensed onto the polyacrylate block in the pure diblock copolymer solution, which is consistent with the formation of polyion complex micelles triggered by counter-ion release in the presence of oligochitosan. The formation of oligochitosan/PAA-PEO core-corona micelles has been investigated by dynamic light scattering (DLS), small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). A minimum length of the PAA block is necessary to ensure micelle formation. The range of pH, where PIC micelles form, critically depends on the PAA block length, which also determines the size of the micelles. Micelles can be dissociated at ionic strength above 0.4 mol L-1. Since these PIC micelles have been used as recyclable structuring agents for the formation of ordered mesoporous materials, the reversibilty of the assembling process was studied upon pH and ionic strength cyclic variations. A hysteresis of stability was observed at low pH, probably due to hydrogen bonding