N-halamine copolymers for use in antimicrobial paints

A series of copolymers containing units of a novel hydantoinylacrylamide and the sodium salt of 2-(acrylamido)-2-methylpropanesulfonic acid have been synthesized. The homopolymer of the hydantoinylacrylamide compound was insoluble in water, while the copolymers with the sulfonic acid sodium salt were water-dispersible/soluble, with the solution becoming completely transparent when the feed ratio for the copolymer contained 7 parts of the hydantoin moiety to 3 parts of the sodium sulfonate moiety. The polymers were added into a commercial water-based latex paint, and upon drying, the painted surfaces treated with the water-miscible copolymers were rendered antimicrobial following chlorination with dilute household bleach. The chlorinated homopolymer failed to provide an antimicrobial property for the paint because of its tendency to isolate into aggregates in the paint, while the completely miscible copolymers were capable of 6-log inactivation of Staphylococcus aureus and Escherichia coli O157:H7 within 5 min of contact time.     

Regenerable antimicrobial silica gel with quaternarized N-halamine

A novel regenerable antimicrobial silica gel was prepared by a dehydration between silanols of silica gel and hydrolyzed 3-chloropropyltrimethoxysilane, a quaternization between grafted hydrolyzed 3-chloropropyltrimethoxysilane and (5,5-dimethylhydantoinyl-3-ylethyl)-dimethylamine (DHEDA), and a chlorination of amide groups of DHEDA. The as-prepared antimicrobial silica gel was characterized by FT-IR and X-ray photoelectron spectroscopy. Antimicrobial tests showed that the as-prepared antimicrobial silica gel was capable of about a 6-log inactivation of Staphylococcus aureus and Escherichia coli O157:H7 within 10 min of contact. Interestingly, more than 2 × 10⁴ CFU/mL of Escherichia coli O157:H7 could be almost inactivated under flowing water condition. Furthermore, the as-prepared antimicrobial silica gel exhibits good regenerability and storage stability.     

卤胺化合物改性壳聚糖/TiO2抗菌复合膜的制备

将5,5-二甲基海因接枝到壳聚糖上,添加TiO2,用涂膜的方法制备复合膜。比较分析了不同参数条件下的氯含量高低,得出最佳工艺参数,然后按照最佳工艺参数制备复合膜,对复合膜进行了SEM和XRD表征,分析了其紫外稳定性及抗菌性能。结果显示:TiO2可均匀分布在复合膜中,TiO2的加入可以明显地提高复合膜的紫外光稳定性。氯化后的复合膜(氯含量为8.17×1020atom/cm2)对金黄色葡萄球菌和大肠杆菌有很好的杀菌效果(10min可以全部杀死7.1log的金黄色葡萄球菌和99.33%的大肠杆菌),该复合膜可用于食品包装材料及生物医药等方面。     

环状卤胺化合物改性壳聚糖/PVA纳米纤维的制备与表征

以易于纺丝的聚乙烯醇(PVA)为纤维基材,添加3-环氧丙基-5,5-二甲基海因改性壳聚糖(CTS-GH),利用静电纺丝法制备出具有高效抗菌效果的纳米纤维。采用扫描电镜、红外光谱、热重分析仪表征和分析了纳米纤维的结构和热性能,考察了纺丝液流量对纳米纤维结构和氯含量的影响。结果表明,纳米纤维的直径随着纺丝速度的加快而减小。利用碘量法测定了纳米纤维的氯含量,说明该纳米纤维经过氯化处理后具有很好的抗菌效果。该纳米纤维可用于抗菌过滤材料、生物医药等方面。     

Pyramidal yield criteria for epoxides

The tensile, compressive and shear yield strengths of two epoxides were measured under superposed hydrostatic pressure extending to 300 MN m^–2. For both materials, the ratio of the moduli of the tensile, _T, to compressive, _C, yield stress at atmospheric pressure was approximately 34, as has been reported previously for a number of thermoplastics. The ₂= ₃ envelope in stress space was plotted according to these two-parameter ( _C and _T) yield criteria: conical, paraboloidal and pyramidal; the best correlation was with the last. The experimental tensile and compressive data for tests under pressure, however, fit slightly better two straight lines which are consistent with a three-parameter single hexagonal pyramidal yield surface. For plane stress and shear under pressure yield envelopes of these surfaces, the correlation with experimental data is again best for the pyramidal criteria, except for biaxial or triaxial tension when these resins are brittle. The third independent parameter employed in the pyramidal criterion was the equi-biaxial compressive yield stress, determined by tensile experiments under appropriate superposed hydrostatic pressure; alternatively plane strain compressive yield stress, _PC, may be used.     

卤胺改性壳聚糖/PVA抗菌复合膜的制备及性能?

壳聚糖具有良好的生物降解性、生物相容性、抗菌性等优异性能,受到研究者们的广泛关注.在前期研究的基础上,将卤胺改性壳聚糖(CTS-GH)与聚乙烯醇(PVA)进行物理混合,制备不同比例的复合膜,以提高卤胺改性壳聚糖膜的实际应用价值.利用原子力显微镜(AFM)考察了两者在溶液中的混合性质;采用扫描电镜(SEM)、示差扫描量热仪(DSC)、X射线衍射(XRD)对复合膜进行了表征;测试了经过氯化处理后复合膜的抗菌性能.结果表明,除 CTS-GH/PVA＝10/90外,均能得到混合性能良好的复合膜.经过氯化处理后,氯含量为0．86×1018个原子/cm2(CTS-GH/PVA＝20/80)的复合膜可在5 min内杀死98．92％金黄色葡萄球菌和100％大肠杆菌,60 min 接触后可杀死100％金黄色葡萄球菌.     

Polymeric materials

Summary The Polymer Section of the Santa Barbara Workshop on Modeling of Materials is briefly reviewed. Motivation and need for modeling in polymer-based materials are outlined and the recommendations resulting from the workshop reported.     

Polymeric photovoltaic materials

Recent developments in conjugated polymer-based photovoltaic elements have been reviewed. The photophysics of such photoactive devices is based on the photoinduced electron transfer from donor-type semiconducting conjugated polymers onto acceptor-type conjugated polymers or acceptor molecules such as Buckminsterfullerene, C₆₀. Photoinduced electron transfer in solid composite films of fullerenes embedded into conjugated polymers is reversible, ultrafast (within 300 fs) with a quantum efficiency approaching unity, and metastable. Similar to the first step in natural photosynthesis, this photoinduced electron transfer leads to a number of potentially interesting applications, which include sensitization of the photoconductivity and photovoltaic phenomena. Furthermore, using the conjugated polymer donors in polymer blends with another conjugated polymer acceptor, similar photovoltaic elements have been realized. Examples of photovoltaic architectures are discussed with their potential in terrestrial solar energy conversion.     

Modifying Fe3O4-functionalized nanoparticles with N-halamine and their magnetic/antibacterial properties

Magnetic/antibacterial bifunctional nanoparticles were fabricated through the immobilization of antibacterial N-halamine on silica-coated Fe(3)O(4)-decorated poly(styrene-co-acrylate acid) (PSA) nanoparticles. The samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), X-ray diffraction (XRD), energy-dispersive X-ray spectrometry (EDX), Fourier transform infrared (FTIR), and thermogravimetric analysis (TGA). The N-halamine was developed from the precursor 5,5-dimethylhydantoin (DMH) by chlorination treatment, and experimental results showed that the loading amount of DMH on the silica-coated Fe(3)O(4)-decorated poly(styrene-co-acrylate acid) nanoparticles was adjustable. The as-synthesized nanoparticles exhibited superparamagnetic behavior and had a saturation magnetization of 18.93 emu g(-1). Antibacterial tests showed that the resultant nanoparticles displayed enhanced antibacterial activity against both Gram-positive and Gram-negative bacteria compared with their bulk counterparts.     

Nanostiffening in Polymeric Nanocomposites

Selected elastic moduli of nanocomposites are higher than the elastic moduli of microcomposites. Molecular immobilization and crystallization at the interfaces had been proposed as potential causes, but studies suggested that these effects are minor and cannot be used to explain the magnitude observed in nanocomposites with >3nm particles. Alternately, molecular simulation of polymer deformation showed that rotation gradients can lead to additional molecular rotations and stiffen the matrix. The stiffening is characterized by the nanostiffening material parameter, l2. In this investigation, an analytical expression for nanostiffening in nanocomposites was developed using finite element analysis. The nanostiffening in nanocomposites was determined by the ratio of l2to the particle size r, and the expression was shown to be in good agreement with experimental data from the literature. The dependence on the ratio suggests that nanostiffening is significant only for nanocomposites with large l2/r but is negligible when l2/r is small.