Synthesis,characterization, thermal stability and antibacterial activity of coumarin based methacrylate copolymers

Monomer of 7-methacryloyloxy-4-methylcoumarin(MAOMC) was synthesized and characterized by FTIR, 1H-NMR and 13C-NMR spectroscopy. Copolymers of MAOMC with butoxyethylmethacrylate(BOEMA) at different feed compositions were prepared by free radical solution polymerization at(70 ± 1) °C in ethylmethylketone(EMK) using benzyl peroxide(BPO) as an initiator. The copolymers were characterized by FTIR and 1H-NMR spectroscopy. Thermogravimetric analysis(TGA) and differential scanning calorimetry(DSC) of the copolymers showed moderate thermal stability and higher Tg values. Gel permeation chromatography(GPC) was used to find out the molecular weights of the different copolymers. Antibacterial activities of the copolymers were also investigated against the selected pathogenic bacteria's. The antibacterial activity of the copolymer increases as the MAOMC content increases in the copolymer. This shows that coumarin moiety plays a very important role in the antibacterial activity.     

SYNTHESIS AND CHARACTERIZATION OF ORGANOMONTMORILLONITE AND POLYAMIDE 66/MONTMORILLONITE NANOCOMPOSITES

The montmorillonites (MMTs), layered, smectite-type silicates, were premodified by two different methods priorto the polymer melt intercalation. In one case MMTs were modified with cetyltrimethylammonium bromide (CTAB), andtermed as organomontmorillonites (OMMTs); in the other case MMTs were modified by nylon, and the products were calledmodified montmorillonites (MMMTs). The effects of CTAB and nylon on the MMTs were investigated by using TG andWAXD. The results show that interlayer spacings of CTAN and nylon modified MMTs are larger than that of sodium MMTs.Then, polyamide 66 (PA 66)/MMT nanocomposites were obtained through the method of melt intercalation of polymers. Thenanocomposites were characterized by WAXD, TEM and Molau experiments. The results indicate that the MMTs dispersehomogeneously in the PA 66 matrix. The mechanical properties of nanocomposites, such as tensile properties and flexuralproperties, were also measured and show a tendency to increase with increase of MMT content and reach the maximumvalues at 5phr MMT content. The heat distortion temperature (HDT) of the nanocomposites (7 phr) is about 32 K higher thanthat of pure PA 66.     

Synthesis of hydroxyl-terminated polybutadiene possessing high content of 1,4-units via anionic polymerization

<正>The hydroxyl-terminated polybutadiene(HTPB) possessing high content of 1,4-units was synthesized by anionic polymerization of butadiene,using alkyllithium containing silicon-protected hydroxyl group as initiator and cyclohexane as solvent.The polymers were characterized by GPC,IR and ~1H-NMR.The mechanical properties of cured films were also evaluated.The results show that the content of 1,4-units for HTPBs made by anionic polymerization reaches up to 90%.The molecular weight distribution is very narrow(≤1.05).The functionality of hydroxyl groups approaches 2.Compared with free radical HTPB,the elongation at break of anionic HTPB films increased by 70%,while the tensile strength remained nearly unchanged.This new HTPB can be very useful in solid propellant.     

Influence of Glycerol Content on Properties of Wheat Gluten/Hydroxyethyl Cellulose Biocomposites

Environmentally friendly biocomposites were prepared by blending wheat gluten（WG）as a matrix, hydroxyethyl cellulose（HEC）as a filler,and glycerol as a plasticizer,followed by thermo-molding of the mixture at 120°C for crosslinking the matrix.Moisture absorption,tensile properties,dynamic mechanical analysis,and dynamic rheology were evaluated in relation to the glycerol content.Tensile strength and modulus drop dramatically with increasing glycerol content,which is accompanied by significant depression in the glass transition temperature and improvement in the extensibility of the biocomposites.     

Mixed matrix membranes of polysulfone/polyimide reinforced with modified zeolite based filler: Preparation,properties and application

In this work,polysulfone/polyimide (PSf/PI) mixed matrix membranes were fabricated by reinforcement of modified zeolite (MZ) particles through solution casting method for investigation of antibacterial activity against two gram negative bacteria (Salmonella typhi,Klebsellapneumonia) and two gram positive bacteria (Staphylococcus aureus,Bacillus subtilis).The modified zeolite particles were incorporated to PSf and PI matrix and the influence of these particles on thermal,mechanical and structural properties was evaluated.The morphological evolution was investigated through scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis,which revealed good compatibility between organic polymer matrix and inorganic filler.Mechanical stability was investigated by tensile testing while thermal analysis was evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC).This revealed improvement in thermal properties with increasing filler concentration from 1 wt％ to 10 wt％.Structural analysis was successfully done using X-ray diffraction analysis (XRD) and Fourier transform infrared (FTIR) spectroscopy.Solvent content of fabricated mixed matrix membranes was observed to decrease while moving from more hydrophilic to less hydrophilic solvent.However,addition of filler content enhanced the porosity of fabricated membranes.The synthesized mixed matrix membranes exhibited good antibacterial activity and the highest activity was shown by PSf/PI/MZ mixed matrix membrane.Therefore,the combination effect of PSf,PI and MZ sufficiently enhanced the antibacterial activity of mixed matrix membranes.     

STUDY ON CASTOR OIL POLYURETHANE/POLY (METHYL METHACRYLATE) AB CROSSLINKED POLYMERS

Castor oil polyurethane/poly(methyl methacrylate) AB crosslinked polymers (ABCP) were synthesized by free radical copolymerization of MMA and vinyl-terminated castor oil polyurethane which was obtained from isocyanate-terminated castor oil polyurethane and hydroxyethyl methacrylate The mechanical properties, transition and relaxation, as well as compatibility and morphology of the ABCP were investigated by changing the component. The results show that the ABCP is a semicompatible system and the compatibility of the two components decreases with increasing content of the hard segment. The mechanical and damping properties of the ABCP are obviously superior to that of their homopolymers. The damping value is mainly controlled by cross[ink density of the ABCP but the T-g value by component.     

Influence of siloxane co-segment length and content of waterborne polysiloxane-urethane copolymers on their water resistance, thermal stability and mechanical properties

<正>A series of stable waterborne polysiloxaneurethane(WPSUR) dispersions were prepared using amino-terminated polydimethylsiloxane(NS),dimethylolpropionic acid(DMPA),castor oil,polypropylene glycol and toluene diisocyanate. Meanwhile,NS with different molecular weights was synthesized and used as the soft co-segment.Effects of types and contents of soft co-segments as well as chain extenders on the thermal degradation and stability for WPSUR films were examined.Results reveal that WPSUR films exhibit excellent water resistance and mechanical properties as compared with pure polyurethane(PU) films,and the NS soft co-segment possesses a remarkable effect on the second stage(stageⅡ),while the content of the hard segment is propitious to the initial stage(stageⅠ).Moreover,the highest temperature of stageⅡ(T_(2m)) for WPSUR films using NS as soft co-segment is 413℃,approximately being 30℃higher than that of those typical PUs using HDA and APDMS as the chain extenders,respectively.     

Mechanical Properties of PPV Film in Thermal Elimination Process

This paper deals with the relationships between the structure of poly（p-phenylene vinylene）（PPV） film and treatment temperature and their mechanical properties.The chemical structures and aggregated structures of PPV precursor（PPVpre） and PPV treated at three node temperatures（125,155 and 230 ℃） were investigated by FTIR spectrometry and X-ray diffraction.The results show that the content of trans-conformation and the size of the crystalline domains increased with the increase of treatment temperature.The mechanical performances of the corresponding polymers were studied by nanoindentation.The elastic modulus and hardness of PPV films decreased with the increases of the content of trans-conformation and the size of the crystalline domains.These results suggest that the conformation and the size of the crystalline domains are able to induce the elastic modulus and hardness variation of PPV films.     

High immobilization of antibacterial moieties onto monodisperse microspheres by dispersion polymerization using bicationic viologen surfmer

In order to achieve monodisperse particles with high content of antibacterial groups covalently bonded on surface, a bicationic viologen,N-hexyl-N’-(4-vinylbenzyl)-4,4’-bipyridinium bromide chloride(HW) was devised as a surfmer in dispersion polymerization of styrene(St) using a mixture of methanol(or ethylene glycol) and water as media.Effects of content of HW,its addition profile and composition of reaction media on particles size and incorporation of HW moieties were mainly investigated.The attachment of silver and gold nanoparticles on particle surface under UV irradiation ascertained the surface-bonded HW segments.SEM,TEM observations and XPS,zata potential measurements indicated that increase of initial HW contents and addition of HW(when polymerization had been performed for 3 h) led to grown particles and enhanced immobilization of HW moieties.Using a mixture of ethylene glycol and water as reaction media, small particles(520-142 nm) with highly attached HW moieties were prepared.Furthermore,antibacterial efficacy of the resultant particles against S.aureus was assayed,and particles with more HW moieties anchored on surface demonstrated greater efficiency of antibacterial activity.     

Polymer-clay nanocomposites: chemical grafting of polystyrene onto Cloisite 20A

An account of the experiments on preparing polystyrene(PS) nanocomposites through grafting the polymer onto organophilic montmorillonite is reported.Cloisite 20A was reacted with vinyltrichlorosilane to replace the edge hydroxyl groups of the clay with a vinyl moiety.Because the reaction may liberate HC1,it was performed in the presence of sodium hydrogencarbonate to prevent the exchange of quaternary alkylammonium cations with H~+ ions.Only the silanol groups on the edge of the clay react with vinyltrichlorosilane.The radical polymerization of the product with styrene as a vinyl monomer leads to chemical grafting of PS onto the montmorillonite surface.The homopolymer formed during polymerization was separated from the grafted organoclay by Soxhlet extraction.Chemical grafting of the polymer onto Cloisite 20A was confirmed by infrared spectroscopy.The prepared nanocomposite materials and the grafted nano-particles were studied by XRD.Exfoliated nanocomposites may be obtained for 0.5 wt%-l wt%clay content.The nanocomposites were studied by thermogravimertic analysis(TGA) dynamic thermal analysis(DTA) and dynamic mechanical analysis (DMTA).     

High strength cellulose composite films reinforced with clay for applications as antibacterial materials

High strength cellulose composite films with antibacterial activities were prepared by dispersing montmorillonites (MMT) into cellulose solution in LiOH/urea aqueous solvent followed by regeneration in ethanol coagulation bath, and then by soaking in 5 wt% hexadecylpyridine bromide ethanol solutions to induce the antibacterial action. The cellulose/MMT composite films were characterized by field emission scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, FTIR, UV-spectra, wide angle X-ray diffraction and mechanical test. The results revealed that MMT was dispersed well in the cellulose matrix to form layer structure with a thickness of approximately 3 nm. The mechanical properties of the cellulose/MMT composite films were significantly improved to achieve 132 MP for tensile strength as a result of the MMT delamination. The hexadecylpyridine bromide was fixed well in the cellulose/MMT matrix through cation exchange, leading to the excellent antibacterial activities against Staphylococcus aureus and Escherichia coli, which is important in their practical applications.     

Preparation,Characterization and Antibacterial Property Analysis of Cellulose Nanocrystals (CNC) and Chitosan Nanoparticles Fine-Tuned Starch Film

To improve the mechanical and antibacterial properties of traditional starch-based film, herein, cellulose nanocrystals (CNCs) and chitosan nanoparticles (CS NPs) were introduced to potato starch (PS, film-forming matrix) for the preparation of nanocomposite film without incorporation of additional antibacterial agents. CNCs with varied concentrations were added to PS and CS NPs composite system to evaluate the optimal film performance. The results showed that tensile strength (TS) of nanocomposite film with 0, 0.01, 0.05, and 0.1% (w/w) CNCs incorporation were 41, 46, 47 and 41 MPa, respectively. The elongation at break (EAB) reached 12.5, 10.2, 7.1 and 13.3%, respectively. Due to the reinforcing effect of CNCs, surface morphology and structural properties of nanocomposite film were altered. TGA analysis confirmed the existence of hydrogen bondings and electrostatic attractions between components in the film-forming matrix. The prepared nanocomposite films showed good antibacterial properties against both E. coli and S. aureus. The nanocomposite film, consist of three most abundant biodegradable polymers, could potentially serve as antibacterial packaging films with strong mechanical properties for food and allied industries.     

Cornstarch/Poly(vinyl alcohol) Biocomposite Blend Films: Mechanical Properties,Thermal Behavior,Fire Retardancy,and Antibacterial Activity

In the present study, biocomposite films of starch/poly(vinyl alcohol) (St/PVA) reinforced with delignified Grewia optiva fiber and methyl methacrylate (MMA) grafted fibers were prepared using citric acid as a plasticizer and glutaraldehyde as the cross-linker. The biocomposite films were subjected to evaluation of mechanical properties, biodegradability, and antibacterial properties. The biocomposite films were characterized by using Fourier transform-infrared (FT-IR) spectrophotometry, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA/DTA/DTG). SEM showed good adhesion between St/PVA blend matrix and fibers. The antimicrobial activity of biocomposite films against pathogenic bacteria such as Staphylococcus aureus and Escherichia coli was also explored. The results confirmed that the biocomposite films may be used for food packaging.     

Preparation and characterization of antibacterial cobalt-exchanged natural zeolite/poly(vinyl alcohol) hydrogels

In the present study, potential application of the local clinoptilolite-rich natural zeolite in formulation of antibacterial hydrogels was investigated. The zeolite powder exchanged with cobalt(II) ions was used in preparation of the zeolite/poly(vinyl alcohol) hydrogel films in different amounts. The films were physically crosslinked by the freezing-thawing method and characterized for their crystallinity, surface and cross sectional morphology, chemical composition, thermal behaviour, mechanical properties, swelling and dissolution behaviours, and antibacterial activities against a Gram-negative bacteria. The films with 0.48 wt% and higher cobalt-exchanged zeolite contents showed antibacterial activity. Addition of the zeolite powder in the formulations did not cause significant changes in the other properties of the films.     

Preparation and characterization of polyvinyl alcohol/β‐cyclodextrin/GO‐Ag nanocomposite with improved antibacterial and strength properties

In this work, new hydrogel films based on polyvinyl alcohol (PVA) and β‐cyclodextrin (β‐CD) were prepared with the aim of studying their ability as an antibacterial and drug carrier system. Gallic acid (GA) was used as an antibacterial drug which was encapsulated into the β‐CD cavity, and finally, β‐CD inclusion complex (GA/βCD‐IC) was prepared. On the other hand, silver nanoparticles (AgNPs) were synthesized on the graphene oxide (GO) surface (GO‐Ag), and the obtained GO‐Ag was used to enhance the antibacterial properties and mechanical strength of their films. FT‐IR and DSC analysis approved the formation of cross‐linking with glutaraldehyde between the PVA and β‐CD. Hydrogel films were characterized using XRD and SEM. The disc diffusion method showed the antibacterial activity for the films containing GO‐Ag and GA. Due to the good strength, elasticity, WVP, and swelling ability, PVA/GA/βCD‐IC/GO‐Ag can be proposed as a potential antibacterial drug delivery system.     

The effect of preparation temperature on the mechanical and antibacterial properties of poly(vinyl alcohol)/silver nitrate films

There has been a growing interest in developing antibacterial polymeric materials. The logical consequence following development of a new material is optimisation of its processing conditions and investigation of the influence of processing parameters on functionality of a given material. The present work deals with investigation of the effect of preparation temperature on the mechanical and antibacterial properties of polymer films based on poly(vinyl alcohol) (PVA) and silver nitrate (0, 1, 3, 5, 7, 9 wt.% silver content). The mechanical properties of the films prepared at various temperatures (25, 35, 50, 60, 75 °C) were characterized by using stress-strain analysis. Antibacterial properties were determined by using an agar diffusion test and a dilution and spread plate technique against both Gram positive (Staphylococcus aureus) and Gram negative (Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumoniae). The results show significant effect of the elevated temperature on the samples properties.     

Preparation and Characterization of Nanocomposite Films from Chitin Whisker and Waterborne Poly(ester-urethane) With or Without Ultra-Sonification Treatment

Two series of nanocomposite films were prepared from waterborne poly(ester-urethane) and chitin whisker with and without ultrasound treatment coded as CW/WPU and CHW/WPU, respectively. The effects of ultra-sonification method and chitin whisker content on the chemical compositions, crystallization behavior and miscibility were studied by attenuated total reflection Fourier transform infrared (ATR-FTIR), wide-angle X-ray diffraction (WXRD), dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM). Thermal stability and mechanical properties of the films were measured by thermogravimetric analysis (TGA) and tensile test, respectively. The results revealed that both nanocomposite films exhibited a certain degree of miscibility when chitin whisker content was lower than 30 wt%, resulting in higher thermal stability and tensile strength than the pure waterborne poly(ester-urethane) film. Interestingly, the composite films CW/WPU with ultrasound treatment possessed better miscibility, storage modulus, thermal stability and tensile strength than those without ultrasound treatment over the entire composition range studied here. The difference can be attributed to the relatively higher dispersion level of whisker within poly(ester-urethane) matrix resulting in relatively stronger entanglement and interaction between both components. The ultrasound treatment can effectively improve the miscibility and mechanical properties of the casting nanocomposite films with nano-meter size chitin whisker added. This indicated that the structure, miscibility and mechanical properties of the nanocomposite films depended significantly on the preparation method.     

Long lasting marine antifouling polyurethane coating chemically bonded with poly(hexamethylene guanidine)

In order to protect the marine environment, traditional marine antifouling coatings such as tributyltin (TBT)-based antifouling coatings have been phased out. There is an urgent need to develop environmentally friendly marine antifouling coatings. In this work, the antibacterial poly(hexamethylene guanidine) (PHMG) was introduced into polyurethane (PU) through chemical bond to prepare a green environmentally friendly marine antifouling coating (PU-PHMG). The morphology, antimicrobial properties, mechanical properties and thermostability of the PU-PHMG films were investigated. The antimicrobial rates of PU-PHMG films against E. coli and S. aureus were both more than 99.9% when PHMG content in the films reached 1.0 wt%. The excellent antimicrobial activities can be maintained for more than 90 days due to the non-leaching characteristic of PHMG. The growth of algae was also inhibited on the surface of PU-PHMG films. The PU-PHMG coating is promising for the applications in marine antifouling field.     

Photopolymerized Cellulose Acetate/Poly(Acrylic Acid) Semi-IPN Films for Wound Dressing Applications

In this work, semi-IPN films, composed of cellulose acetate(CA) and crosslinked poly(acrylic acid), have been synthesized via benzophenone (BP) induced free radical photo-polymerization of acrylic acid (AAc) in the presence of dissolved cellulose acetate (CA) using N,N’ methylene bisacrylamise (MB) as the crosslinking agent. The mechanical properties were tested for the films having different compositions of MB, CA and AAc in the feed mixtures. The tensile strength (TS) and percent elongation (PE) were found to increase with a concentration of CA in the films, but showed decreasing trends with concentrations of CA in the films. However, with AAc content in the films, the TS increased and PE showed just the opposite trend. The film samples were also studied for water vapor and oxygen permeation studies. The water vapor transmission rate (WVTR) decreased with MB and CA contents, but showed an increasing trend with AAc contents in the films. Finally, a representative sample showed fair antibacterial and antifungal action against E. coli and Aspergillus flavus when studied using the ‘Zone of inhibition method’.     

壳聚糖/明胶/TiO2三元复合膜的制备与功能特性

纳米TiO2用阴离子表面改性剂SDS改性后,以溶液共混法制备了壳聚糖／明胶/TiO2复合膜,用FTIR、XRD、SEM、TEM表征了其结构与形态,并测试了其吸水率、透光率、力学性能和抑菌性能。进而探讨了复合膜中明胶和纳米TiO2含量对壳聚糖膜性能的影响。结果表明：复合膜中,壳聚糖、明胶和TiO2微粒间存在强烈的氢键相互作用,从而使明胶与壳聚糖具有良好的相容性,TiO2与壳聚糖、明胶分子间有很好的界面作用。适量TiO2的加入,可使壳聚糖／明胶共混膜的力学性能得到改善,明胶质量分数为0．30时,掺杂wTiO2为0．01、0．02的复合膜较壳聚糖／明胶共混膜的湿强及干态韧性分别提高了55．9％,40．8％和49．7％,47．9％。此外,复合膜的抑菌性能随明胶的增加而降低,但随TiO2的掺杂比的增加而增强,纳米TiO2的引入拓宽了壳聚糖和明胶两种天然高分子材料的应用范围。