Synthesis and characterization of poly(2‐methacryloyloxyethyl phosphorylcholine) onto graphene oxide

The polyzwitterionic brushes comprised of poly(2‐methacryloyloxyethyl phosphorylcholine) (pMPC) segments, which are used for surface modification of polymers and biocompatible coatings, were investigated. In this work, reverse surface‐initiated atom transfer radical polymerization (RATRP) of zwitterionic 2‐methacryloyloxyethyl phosphorylcholine (MPC) is employed to tailor the functionality of graphene oxide (GeneO) in a well‐controlled manner and produce a series of well‐defined hemocompatible hybrids (termed as GeneO‐g‐pMPC). The complexes were characterized by FT‐IR, XRD, and Raman. Results show that MPC has been coordinated on the graphene oxide sheet. Thermal stability of the nanocomposites in comparison with the neat copolymer is revealed by thermogravimetric analysis and differential thermal analysis. Scanning electron microscopy and transmission electron microscope images of the nanoconposite displays pMPC chains were capable of existing on GeneO sheet by RATRP. The biocompatibility properties were measured by plasma recalcification profile tests, hemolysis test, and MTT assays, respectively. The results confirm that the pMPC grafting can substantially enhance the hemocompatibility of the GeneO particles, and the GeneO‐g‐pMPC hybrids can be used as biomaterials without causing any hemolysis. With the versatility of RATRP and the excellent hemocompatibility of zwitterionic polymer chains, the GeneO‐g‐pMPC nanoparticles with desirable blood properties can be readily tailored to cater to various biomedical applications. Copyright © 2013 John Wiley & Sons, Ltd.     

Study on Biological Safety of Polyvinyl Alcohol/Collagen Hydrogel as a Tissue Substitute (II)

Physically crosslinked polyvinyl alcohol/collagen composite hydrogels were prepared by a cyclic freezing-drying technique. The biological properties of the hydrogels, including hemolysis, anaphylaxis, pyrogen and acute systemic toxicity tests and implantation in-vivo, were investigated. The hemolysis test suggested that the polyvinyl alcohol/collagen, with a hemolysis index of 1.19%, did not have an obvious hemolysis reaction. There was no toxicosis or death cases observed in the acute systemic toxicity test, and the hydrogel showed no anaphylaxis or pyrogen response. The composite hydrogel showed a good histological compatibility in the in-vivo study. The results indicated that the polyvinyl alcohol/collagen composite hydrogels have promising applications for pharmaceutical and biomedical fields.     

Preparation,Characterization and Drug Release Behavior of 5-Fluorouracil Loaded Carboxylic Poly(ε-caprolactone) Nanoparticles

In this paper, 5-Fluorouracil (5-FU) loaded carboxylic poly(ε-caprolactone) nanoparticles have been prepared by emulsification/solvent evaporation o/w method, and the drug release behaviors of 5-FU were investigated. The novel carboxylic poly (ε-caprolactone) (P(CL-OPD)-mal) was synthesized via conjugation of maleic anhydride to sodium borohydride (NaBH₄) reduced poly(ε-caprolactone-co -4- carbonyl -ε-caprolactone) (P(CL-OPD)), while P(CL-OPD) was synthesized in bulk by ring-opening polymerization of ε-caprolactone and 4-carbonyl-ε-caprolactone (OPD) with stannous octoate as a catalyst. Their structures were confirmed by ¹HNMR, FT-IR and GPC. Dynamic light scattering (DLS), transmission electron microscopy (TEM), zeta potential measurements were used for nanoparticle characterization. TEM and DLS showed the nanoparticles were with spherical shape and uniform size distribution (mean diameter 70～100 nm), respectively. Zeta potential analysis revealed that the nanoparticles had an increased negative surface with the increase of carboxyl group concentration. UV spectroscopy was adopted to study the entrapment and release behaviour. The maximum 5-FU loading efficiency was 14.39% with the entrapment efficiency be 42%. In vitro release studies were performed in PBS at 37°C. Results of the study showed that the release behavior can be well-controlled, and the balanced release was up to 96 h. P(CL-OPD)-mal nanoparticles would provide increased benefit in biomedical and pharmaceutical applications.     

Novel Bis-arylPheDOT Synthons for Electrochromic Polymers

Two terthiophenes incorporating the synthon 3,4-(1,2-phenylenedioxy)thiophene (PheDOT) have been developed. Specifically, 2,5-bisthienyl-3,4-(1,2-phenylenedioxy)thiophene (BTh-PheDOT 1) and 2,5-bisethylenedioxythienyl-3,4-(1,2-phenylenedioxy)thiophene (BEDOT-PheDOT 2) were electropolymerized to form electroactive polymer films (P1 and P2) that switched between two highly colored states with the more electron-rich EDOT derivative P2 observed to switch at a lower potential. Additionally, both P1 and P2 displayed moderate to low optical bandgaps of 1.8 and 1.6 eV, respectively. Crystal structures of BTh-PheDOT showed the monomer to be nearly planar with π -stacking observable between monomers. These findings demonstrate the potential of PheDOT as an electroactive synthon for the formation of well-ordered systems.     

Anti‐static Agent Containing Zinc Oxide and its Modification for PA6 Fiber

A new anti‐static agent was synthesized from zinc oxide‐adipic acid‐polyethylene glycol and caprolactam by three‐step reactions. The antistatic agent (called poly(ether ester amide zinc oxide) or PEEAZ) was analyzed by IR and DSC. The results showed that zinc oxide existed in the main chain of PEEAZ. The glass temperature and melt temperature of poly(ether ester amide zinc oxide) (referred to as PEEAZ in the following) decreased with increasing poly(ether ester zinc oxide) increasing in PEEAZ. Antistatic PA6 fiber was obtained by adding PEEAZ 2–8% (wt/wt) to PA6 during blend spinning. The specific resistance and the static half‐value period of PA6 fiber was less than 10⁹Ω · cm and 60 sec, respectively. Excellent antistatic property remained after being washed 30 times.     

Cyclopentadienyl(iron)arene-bis-(p-N,N-dimethylaminobenzylidene)-cyclopentanone Photoinitiated Polymerization of Methyl Methacrylate and Styrene

Abstract

Polymerization of methyl methacrylate and styrene can be effectively photoinitiated by a binary photoinitiator system consisting of cyclopentadienyl(iron)arene hexafluorophosphonate salt and bis(p-N, N-dimethylaminobenzylidene)cyclopentanone in the spectral range of 400–500 nm. The amine-type radical formed from the exciplex of the binary photoinitiator system is probably responsible for the radical polymerization of vinyl monomers. A probable mechanism of initiation of polymerization is discussed.     

Effects of Reaction Conditions on the Plasma Polymerization of Ethylene

Abstract

Ehylene can be polymerized at low pressures in a radio-frequency glow discharge. The form of the resulting polymer may be a powder at low pressure (1 to 2 Torr) and low monomer feed rate (10 to 40 cc/min), a colorless film at low pressure and high feed rate (70 to 90 cc/min), or an oil at high pressure (4 to 5 Torr) and high feed rate. The powder and film forms of plasma-polymerized ethylene are insoluble in common organic solvents, indicating a highly cross-linked structure. The oily products, however, are soluble in acetone and xylene. Chemical evidence indicates that the oil is most likely composed of highly branched oligomers of ethylene. Mass spectrometric analysis of the gaseous effluents show that under film-forming conditions the only hydrocarbon species observable are those derived from ethylene. The powder- and oil-forming conditions, on the other hand, yielded oligomeric species. On the basis of this evidence, a mechanism for the plasma-polymerization of ethylene is proposed.     

Flammability and Thermal Oxidative Degradation Kinetics of Magnesium Hydroxide and Expandable Graphite Flame Retarded Polypropylene Composites

The flammability and the thermal oxidative degradation kinetics of expandable graphite (EG) with magnesium hydroxide (MH) in flame‐retardant polypropylene (PP) composites were studied by limiting oxygen index (LOI), UL‐94 test, and thermogravimetric analysis (TGA). The results show that EG is a good synergist for improving the flame retardancy of PP/MH composite and the effect is enhanced with decreasing EG particle size. The Kissinger method and Flynn‐Wall‐Ozawa method were used to determine the apparent activation energy (E) for degradation of PP and flame retarded PP composites. The data obtained from the TGA curve indicate that EG markedly increases the thermal degradation temperature of PP/MH composites and improves the thermal stability of the composites. The kinetic results show that the values of E for degradation of flame retarded PP composites is much higher than that of neat PP, especially PP/MH composites with suitable amount of EG, which indicates that the flame retardants used in this work have a great effect on the mechanisms of pyrolysis and combustion of PP.     

Multi-responsive cyclodextrin vesicles assembled by ‘supramolecular bola-amphiphiles’

Multi-responsive cyclodextrin vesicles (CDVs) self-assembled by ‘supramolecular bola-amphiphiles’, consisting of a guest (N,N′-bis(ferrocenylmethylene)-diaminohexane, 1) and a host (γ-hydroxybutyric-β-cyclodextrin, γ-HB-β-CD), were prepared and investigated for the first time. The morphologies and sizes of these novel vesicles in water were observed by transmission electron microscopy (TEM), scanning electron microscopy and dynamic light scattering. The effects of the host–guest ratio, the concentration and the solvent composition are also discussed. The host–guest interactions, complex stoichiometry and structures of 1·γ-HB-β-CD in water were investigated by cyclic voltammetry, UV and NMR spectroscopy. According to the complex stoichiometry, TEM observations and Chem3D estimation, the ‘supramolecular bola-amphiphiles’, made from 1·γ-HB-β-CD and assumed for the first time, formed the membranes of the CDVs. The CDV system was responsive to an oxidising agent, which is the first report on redox-responsive systems in this field. The CDVs are also responsive to pH and the presence of metal ions, such that they disassemble upon addition of acetic acid or Cu²⁺ ions, providing possible routes to drug delivery systems.     

Microcalorimetry study on the microbial activity of permafrost on the Tibetan plateau of China

Microcalorimetric techniques had been used to study the influence of different physicochemical parameters on microbial growth in different permafrosts on the Tibetan plateau. The total heat evolution of the permafrost samples amended with glucose, Q _T , the values of microbial growth rate constant, k, and the heat output power, P _t , were calculated from the power–time (P–t) curves. It is observed that the same coverage vegetation show similar P–t curves, which strongly suggest that the permafrost microorganisms of the homology vegetation coverage have similar structures of community. Furthermore, the vegetation degradation turns out to have significant influence, that is, the better the status of vegetation is, the higher the values of k, CFU and Q _T are.