高分子多孔膜的表面改性与抗污染研究

采用羟基化预处理、铈盐引发和碱化预处理、Fe2 /H2O2引发两种引发体系,对聚砜(PS)膜和聚丙烯腈(PAN)膜进行表面接枝丙烯酰胺的改性,研究预处理和表面接枝改性对膜污染的影响。采用红外光谱和X光电子能谱对羟基化和接枝改性的膜表面进行表征。研究表明,表面预处理和接枝后,PS膜和PAN膜的水通量均有所下降,但提高了抗牛血清蛋白膜污染能力。     

Free‐radical grafting of acrylic acid onto isotactic polypropylene using styrene as a comonomer in supercritical carbon dioxide

Free‐radical grafting of acrylic acid (AAc) onto isotactic polypropylene (iPP) using styrene (St) as a comonomer in supercritical carbon dioxide (SCCO₂) medium was studied. The effects of temperature and pressure of reaction on functionalization degree (grafting degree of AAc) of the products were analyzed. The increase of reaction temperature increases the diffusion of monomers and radicals in the disperse reaction system of SCCO₂. In addition, the increase of temperature accelerates the decomposition rate of 2,2′‐azobisisobutyronitrile (AIBN), thus promoting grafting reaction. It was also observed that functionalization degree of the products decreases with the increase of pressure of SCCO₂ in the range of experiment. The effects of comonomer St on the functionalization degree of the products were investigated. The AAc graft degree of the resulting polymer was drastically higher in the present of St. It reached a maximum when the mass ratio of St and AAc was about 0.7 : 1. Because AAc is not sufficiently reactive toward iPP macroradicals, it would be helpful to use a second monomer that can react with them much faster than AAc. St preferentially reacts with the iPP macroradicals to form more stable styrene macroradicals, which then copolymerize with AAc to form branches. The highest functionalization degree was obtained when the AIBN was 0.75 wt %. When the initiator was used excessively, the functionalization degree decreased because of severe chain degradation of the iPP backbone. The morphologies of pure iPP and grafted iPP are different under the polarizing optical microscope. The diameter of the pure iPP spherulites is 20–38 μ and that of the grafted iPP spherulites is reduced with the increase of the functionalization degree of the products. This is proposed to be because the polar grafts formed during the reaction would have a tendency to associate in the hydrophobic PP environment. This might preserve some of the local crystalline order that existed during the reaction in the swollen iPP phase. It can be proven by a DSC cooling investigation that the crystallization temperature increased as the functionalization degree increased. This is proposed to be because the side‐chain of grafting polymer helps to bring about the heterogeneous nucleation in grafting polymer. Therefore, a large number of nuclei can emerge to a lesser supercooling degree. It can be also proven that the percent crystallization decreased as the functionalization degree increased, probably due to the grafted branches, which disrupted the regularity of the chain structure and increased the spacing between the chains. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2203–2210, 2004     

硅烷偶联剂的种类与结构对二氧化硅表面聚合物接枝改性的影响

在超细二氧化硅表面接枝聚合改性工艺的基础上,通过透射电子显微镜、红外光谱、X射线光电子能谱等检测手段,并结合模型计算,研究了硅烷偶联剂(silane coupling agent)对超细二氧化硅表面聚合物接枝改性的影响及其机理。认为硅烷偶联荆KH570和KH858都是有效的预处理剂,硅烷偶联剂的种类对改性影响很大。由于KH570中含有的双键与羰基形成了离域II4^4键,使其双键结合力减弱;而在KH858中由于硅原子的供电子效应,使其双键结合力有所加强;使用KH570预处理的超细二氧化硅表面含有的聚合物更多,分散性更好。KH570更适合用作超细二氧化硅表面接枝聚合改性的预处理剂。     

骨组织工程支架材料磷酸钙双相生物陶瓷的研究进展

双相磷酸钙(biphasic calcium phosphate,BCP)生物陶瓷材料在整型外科领域是一类重要的骨修复材料。该材料由稳定相羟基磷灰石(hydroxyapatite,HA)和可溶解相β-磷酸三钙(β-tricalcium phosphate,β-TCP)双相平衡优化得到,其生物活性及生物降解性可调。模拟人体自然骨结构的多孔型BCP适宜细胞及骨组织的长入,是一类优异的骨组织工程支架材料。概述了BCP生物陶瓷材料的研究历史、制备工艺及材料表征;评价了多孔型BCP陶瓷的孔隙结构、力学性能及生物学性能;综合了多孔型BCP陶瓷作为骨组织工程支架材料的研究方向;并展望了组织工程化的BCP支架材料的研究未来。     

Tailoring bulk and surface grafting of poly(acrylic acid) in electron-irradiated PVDF

Endowing conventional hydrophobic poly(vinylidene fluoride) (PVDF) films with hydrophilic properties was conducted using electron beam irradiation. Grafting of acrylic acid (AA) in/onto pre-irradiated PVDF films was investigated. Reaction parameters, monomer concentration and inhibitor concentration were examined. Radiation grafted films (PVDF-g-PAA) were synthesized with various grafting yields ranging from 12 to 130 wt % in presence of Mohr's salt (25 wt %). Below 80 wt % of monomer concentration, the degree of swelling was found to increase with the grafting yield. The PAA was arranged randomly in all PVDF matrix (grafting through). Above 80 wt % of monomer concentration, the PAA was grafted only onto the surface of PVDF films leading to a highly dense layer of PAA. Grafting through or surface grafting processes were achieved by varying the water fraction in the initial monomer solution. Water molecule acts not only as a carrier for the monomer but also as a plasticizer expanding the film in the three dimensions. Evidences of grafting through and surface grafting were produced using FTIR in ATR mode, SEM coupled to X-ray detection and XPS. An accurate quantification of AA units was possible up to the micromole via a Cu²⁺–EDTA complex analyzed by UV–vis spectroscopy.     

山梨醇类成核剂对改性聚丙烯发泡性能的影响

以过氧化苯甲酰（BPO）为引发剂,经熔融挤出过程将苯乙烯（St）接枝到等规聚丙烯（iPP）上,同时加入山梨醇类成核剂［1,3:2,4二（对甲基卞叉）山梨醇,MDBS］,制备可发泡的iPP,并考查MDBS在其发泡过程中所起的作用。结果发现,St接枝到iPP上,降低了iPP的熔体流动速率,即提高了其熔体强度;在发泡过程中,MDBS起固定泡孔和泡孔成核的作用,使iPP泡沫具有规则完整的泡孔结构,且泡孔密度从纯iPP的1.1×10^7个/cm3增加到1.2×10^8个/cm3,适宜发泡温度范围拓宽至150~160 ℃。     

Synthesis and properties of natural rubber modified with stearyl methacrylate and divinylbenzene by graft polymerization

The graft polymerizations of stearyl methacrylate (SMA) and divinylbenzene (DVB) onto natural rubber (NR) were carried out in a solution process using benzoyl peroxide (BPO) as an initiator in toluene or chloroform. The main products of the grafted NR include an uncrosslinked (sol) part [sol(SMA–NR–DVB): s‐SNRD] and a crosslinked (gel) part [gel(SMA–NR–DVB), g‐SNRD]. s‐SNRD was obtained by extraction using tetrahydrofuran. It was identified by IR and ¹H‐NMR spectroscopies. The glass transition temperature (T_g) and thermal properties of s‐SNRD and g‐SNRD were studied by DSC and TGA. The glass transition temperature and thermal decomposition temperature of s‐SNRD and g‐SNRD were higher than were those of NR. The light resistance and weatherability of s‐SNRD were measured with a Weather‐o‐Meter. The light resistance and weatherability of s‐SNRD are better than are those of NR. The effects of the initiator concentration, mol ratio of SMA to DVB, reaction time, temperature on grafting ratio, and crosslinking ratio were investigated. The highest grafting ratio and crosslinking ratio in the graft polymerization of SMA and DVB onto NR were obtained when the mol ratio of SMA to DVB and BPO were 4.0 and 2 wt %, at 80°C for 48 h, respectively. Following several studies on oil‐absorptive polymers in our laboratory, 9 the oil absorptivity of g‐SNRD was examined using crude oil. The oil absorptivity of g‐SNRD was 600% when the immersion time was 10 min. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2464–2470, 2001     

Curing of epoxy resin by ultrafine silica modified by grafting of hyperbranched polyamidoamine using dendrimer synthesis methodology

Hyperbranched polyamidoamine–grafted silica was prepared according to dendrimer synthesis methodology. The modified silica was dispersed uniformly in epoxy resin, and the curing of epoxy resin proceeded successfully by heating in the presence of the modified silica; the gel fraction of the epoxy resin cured by the hyperbranched polyamidoamine–grafted silica (grafting = 80.2%) reached 77% at 170°C after 48 h. The gel fraction increased with increasing terminal amino group content of the hyperbranched polyamidoamine–grafted silica. In addition, the curing ability of the silica increased by complexation of the terminal amino groups of the grafted polyamidoamine with boron trifluoride. The modulus of elasticity of the curing materials obtained using the modified silica as a curing agent was lower than that using conventional a curing agent such as ethylenediamine in the presence of untreated silica. On the other hand, the heat resistance of the curing product using the modified silica was superior to that using ethylenediamine, but no difference in glass‐transition temperature was observed. It is expected that hyperbranched polyamidoamine grafted‐silica is incorporated uniformly with chemical bonds in the matrix of the epoxy resin. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 573–579, 2001     

Novel regenerable N‐halamine polymeric biocides. III. Grafting hydantoin‐containing monomers onto synthetic fabrics

A novel cyclic‐amine monomer, 3‐allyl‐5,5‐dimethylhydantoin (ADMH) was synthesized and characterized. ADMH alone could not be grafted onto ordinary polymers. However, the presence of triallyl‐1,3,5‐triazine‐2,4,6(1H,3H,5H)‐trione (TATAT) remarkably enhanced the ADMH grafting yield onto synthetic fabrics. The influences of reaction conditions on the grafting copolymerization were investigated. After chlorine bleach treatment, hydantoin units in the grafted copolymers were transformed into N‐halamine structures. Treated samples exhibited potent antibacterial activity against Escherichia coli, and the functional properties were shown to be durable and regenerable. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1517–1525, 2001     

Grafted stock synthesis of ABS at the ultimate high ratio of polybutadiene to poly(styrene‐co‐acrylonitrile)

This study describes the emulsion grafting of styrene and acrylonitrile onto 60–70% polybutadiene (PB), in the presence or absence of tert‐dodecanetiol as a chain transfer reagent with a radical initiator, and the properties of the obtained grafted stock. There was no significant difference in terms of effect of the initiation mode on the grafting efficiency resulting from the high grafting reactivity of PB. However, the grafted stock with 70% PB prepared in the presence of tert‐dodecanetiol and the adequate selection of an initiation system gave a homogeneous dispersion of the PB particles into poly(styrene‐co‐acrylonitrile) (SAN) matrix. The initiation system involves tert‐butyl peroxylaurate, tert‐butyl peroxyacetate, and tert‐butyl peroxyisopropylcarbonate coupled with ferrous sulfate. The efficient coverage of the SAN grafted layer around 70% PB particles was observed by TEM to eventually give excellent impact resistance, high surface gloss, and good thermal resistance. The absence of tert‐dodecanetiol resulted in a toughness reduction of ABS. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3462–3470, 2001