Phase Transition and Micellization of Temperature Responsive Dextran-graft-poly (N-isopropylacrylamide) Polymers

Phase behavior and micellization of dextran-graft-poly (N-isopropylacrylamide) (PNIPAAm) polymers in aqueous solution are investigated in this paper using DSC and AFM methods. It is found that with the increase of grafting (G%) of the copolymers the endothermic enthalpy during the phase transition increases significantly and the transition temperature decreases slightly. The phase transition behavior of the copolymers is scanning rate dependent. Micelles are formed whenever the solution temperature is raised above the LCST of the copolymers. It is proposed that by using this thermal responsive property of the copolymers, drugs could be incorporated into the micelles without employing any organic solvent.

Biocompatible,Hemocompatible and Antibacterial Acylated Dextran-g-polyisobutylene Graft Copolymers with Silver Nanoparticles

The novel amphiphilic acylated dextran-g-polyisobutylene(AcyDex-g-PIB)graft copolymers with different branch lengths(A4nPtB,2600-5800 g/mol)and grafti ng numbers(GN,5-28 per 1000 Dex mono saccharide)were successfully synthesized via the nu cleophilic substitution of the hydroxyl(-OH)side groups along AcyDex backb one by the living PIB-THF4+chai ns prepared through cati onic polymerizatio n.The crystallizati on of AcyDex backb one in AcyDex-g-PIB graft copolymers was con fined due to the prese nee of PIB branches and the morphology changed from short rod-like crystals to fragment-like crystals with increasing Mn P|B and GN.The obvious microphase separation occurred due to the incompatibility between hard AcyDex backbone and soft PIB branches.AcyDex-g-PIB graft copolymers exhibit excellent biocompatibility towards HeLa cells and good hemocompatibility with red blood cells(RBCs),both of which increase with increasing GN.The in creases of water con tact angle and roughness on the surface of the graft copolymers with in creasi ng A4nP|B and GN manifest the anti-protein adsorption performance.The amphiphilic AcyDex-g-PIB graft copolymers could self-assemble in aqueous solution into nanospheres,which can be used as pH-sensitive drug carriers and can release 100%of the loaded drug within 72 h at pH=7.4.AcyDex-g-PIB graft copolymers bearing silver nanoparticles(Ag-NPs,0.8 wt%-3.9 wt%,4.5-9.5 nm)show good antibacterial properties.This kind of amphiphilic graft copolymer would have a promising prospect in biological and medical fields.

SYNTHESIS AND CHARACTERIZATION OF GRAFT COPOLYMERS BASED ON POLY(p-PHENYLENE TEREPHTHALAMIDE) BACKBONE AND WELL-DEFINED POLYSTYRENE SIDE CHAINS

A novel dualfunctional monomer, 2-（2＇,2＇,6＇,6＇-tetramethyl-piperidinyl-1＇-oxy）methylbenzene-1,4-dioyl chloride hydrochloride, with two acid chloride groups for step-growth polymerization and a nitroxide group for the mediation of living radical polymerization was synthesized. It was first copolymerized with terephthaloyl chloride and p- phenylenediamine at a feed molar ratio of 1：3：4 in N-methyl-2-pyrrolidone containing 10 wt% calcium chloride at -10℃ to yield a poly（p-phenylene terephthalamide） based macroinitiator, which initiated radical polymerization of styrene at 125℃ to obtain a series of poly（p-phenylene terephthalamide）-g-polystyrenes. A combinatory analysis of proton nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, elementary analysis, thermogravimetry and gel permeation chromatography indicated that the macroinitiator induced the radical polymerization of styrene to proceed in a well- controlled way. The molecular weight of side-chains increased with an increase of monomer conversion, and the molecular weight distribution index remained lower than 1.5. The graft copolymers showed a remarkably improved solubility in N- methyl-2-pyrrolidone and much depressed crystallinity in bulk.

CHARACTERIZATION OF AMPHIPHILIC AND MICROPHASE SEPARATED GRAFT COPOLYMERS Ⅱ SURFACE CHARACTERIZATION AND IN VITRO BLOOD-COMPATIBILITY ASSESSMENT OF POLYSTYRENE-GRAFT-ω-STEARYLPOLY (ETHYLENE OXIDE)

This paper reported the research results concerning the surface characterization ofpolystyrene-graft-w-stearyl poly(ethylene oxide) (PS-g-SPEO) by means of XPS,contactangle measurement and TEM, and its in vitro blood compatibility assessment by measuringthe plasma recalcification time (RT) and partial thromboplastin time (PTT). The XPSresults demonstrated that the surface and bulk composition of the PS-g-SPEO graftcopolymers differ remarkably from each other,and that SPEO component was constantlyenriched at the copolymer/air interface. Contact angle studies indicated that the surfacewater wettability can be adjusted effectively by changing the composition of the copolymer.PS-g-SPEO graft copolymers can undergo microphase separation as clearly illustrated byTEM photographs. The relationship between the surface properties of PS-g-SPEO graftcopolymer and its blood compatibility was also discussed.

Formation of polymer vesicles by amphiphilic fluorosiloxane graft copolymers in solution

Amphiphilic fluorosiloxane graft copolymers with a poly（dimethylsiloxane） （PDMS） backbone, a hydrophobic fluorosiloxane side-chain and three hydrophilic polyether side-chains were synthesized by hydrosilation reaction in this work. The micellization of amphiphilic graft copolymers in the water/ethanol solvent system was investigated, and vesicles with different size were formed after the self-assembly system was aged for different time.

Performance and synergistic effect of phenolic and thio antioxidants in ABS graft copolymers

The synergistic effect of phenolic and thio antioxidants on the stabilization of acrylonitrile-butadienestyrene(ABS)graft copolymers has been studied.Three commercial antioxidants Irganox245,Irganox1076 and dilauryl thiodipropionate(DLTP)were selected.Formulations based on hindered phenols and secondary antioxidant DLTP were prepared.Stabilization was monitored in terms of changes in the functional groups(oxidation products),tensile properties and yellowness index.Differential scanning calorimetry(DSC)and thermogravimetry(TG)were also used to assess the stability.The results indicated that the combination of Irganox245 and DLTP showed much better stabilization effect than the individual components due to the strong synergistic effect.Only weak synergism could be observed in the formulation that contained Irganox1076 and DLTP.Irganox1076 and Irgnox1076/DLTP exhibited similar behaviors between antioxidants with the highest and lowest efficiencies.

Antibacterial Behaviour of Quaternized Poly(vinyl chloride)-g-Poly(4-vinyl pyridine) Graft Copolymers

Amphiphilic graft copolymers consisting of poly（vinyl chloride）（PVC） main chains and poly（4-vinyl pyridine）（P4VP） side chains were synthesized via atom transfer radical polymerization（ATRP） using direct initiation of chlorine atoms. The successful synthesis of PVC-g-P4 VP graft copolymers was confirmed by Fourier transform infrared spectroscopy（FTIR） and proton nuclear magnetic resonance（1H-NMR）. Transmission electron microscope（TEM） and small angle X-ray scattering（SAXS） analysis showed that PVC-g-P4 VP exhibited microphase-separated, ordered structure with 37.6 nm of domain spacing, which was not observed in neat PVC. For antibacterial applications, the tertiary nitrogen atoms of PVC-gP4 VP was quaternized using 1-bromohexane, as confirmed by FTIR measurements. Bacteria including Escherichia coli（E. coli）, Staphylococcus aureus（S. aureus）, Bacillus cereus（B. cereus）, and Pseudomonas aeruginosa（P. aeruginosa） were completely killed in 24 h on the quaternized PVC-g-P4VP（46% grafting） surface, indicating its excellent antibacterial behavior while it showed to be cytotoxic to mammalian cell.

Effects of Branches on the Crystallization Kinetics of Polypropylene-gPolystyrene and Polypropylene-g-Poly(n-butyl acrylate) Graft Copolymers with Well-defined Molecular Structures

Effects of branches on the crystallization kinetics of polypropylene-g-polystyrene （PP-g-PS） and polypropylene-g- poly（n-butyl acrylate） （PP-g-PnBA） graft copolymers with well-defined molecular structures were systematically investigated by DSC. The Avrami equation was used to analyze the isothermal crystallization process, while the analysis of nonisothermal crystallization process was based on the Jeziorny-modified Avrami model and Mo model. The kinetics results of isothermal and nonisothermal crystallization verified the peculiar effects of branches on the crystallization process of PP backbones in PP-g-PS and PP-g-PnBA graft copolymers： on one hand, the interaction between branches （n-n interaction between PS branches, or dipole-dipole interaction between PnBA branches） restrained the mobility and reptation ability of the PP backbones, which hindered the crystallization process; on the other hand, the heterogeneous nucleation effect resulting from the branched structure and fluctuation-assisted nucleation mechanism （caused by microphase separation between the PS or PnBA rich phase and the PP rich phase） became more pronounced with increasing branch length, which facilitated the crystallization process.

Amphiphilic Graft Copolymers of Hydroxypropyl Cellulose Backbone with Nonpolar Polyisobutylene Branches

The novel amphiphilic graft copolymers with hydrophilic hard polar hydroxypropyl cellulose(HPC)backbone and hydrophobic soft nonpolar polyisobutylene(PIB)branches have been successfully synthesized through nucleophilic substitution reaction of living PIB chains carrying oxonium ions with the-OH groups along HPC backbone.The PIB branch length in the graft copolymers could be designed by living cationic polymerization and the grafting density could be adjusted by PIB+/-OH molar ratio.The living PIB chains carrying oxonium ion were prepared by transformation of allyl bromide end groups in the presence of AgCI0_(4) and silver nanoparticles(3.2±0.3 nm,0.7 wt%-1.8 wt%)generated in situ from AgBr.The phase-separation morphology was formed in the graft copolymers due to their incompatibility between backbone and branches.The hydrophilicity on the surface of graft copolymer films could be turned to hydrophobicity by increasing grafting density or/and length of PIB branches.The soft PIB segments in graft copolymers provided an unique surface wa self-assembly for ant卜protein adsorption against bovine serum albumin.A small amount of Ag nanoparticles in the copolymers contributed to good antibacterial activities against Staphylococcus aureus or Escherichia coli.

Surface Photografting of Novel Sulfobetaine Copolymers on Silica

A couple of novel sulfobetaine copolymer is developed via Michael-type addition reaction. The comonomers, diamines and maleimide react via Michael reaction through UV irradiation using AIBN as photoinitiator producing polyamine chain. Further, sulfobetaine copolymers were obtained on treatment of the polyamine with sulfopropylating agent, 1,3-propane sultone. These novel sulfobetaine polymers were grafted on silica surface to produce responsive biocompatible surface. This easy straightforward, catalyst free facile protocol for synthesis of polymer grafted surface is useful for developing biomedical devices. Additionally, both the copolymers show fluorescence characteristics.

Synthesis and Characterization of Degraded Gelatin Grafted Poly(ε-caprolactone) Copolymers

Hydrophilic degraded gelatin was modified with hydrophobic poly(ε-caprolactone) (PCL) via a chemical grafting route.Firstly,PCL with one hydroxyl end group was prepared by the ring-opening polymerization of εcaprolactone (ε-CL) with tin (Ⅱ) 2-ethylhexanoate as catalyst and n-butyl alcohol as initiator.Secondly,the PCL reacted with isophorone diisocyanate (IPDI) to prepare PCL with isocyanate functional group (PCL-NCO).Hydroxylamine was used to degrade gelatin by the cleavage between asparagine and glycine residues of gelatin.PCL-NCO reacted with the hydroxyl/amino groups of degraded gelatin in a homogeneous system and yielded the PCL modified gelatin copolymers.The gelatin grafted PCL copolymers were measured by means of XRD,FTIR,DSC and 1 H NMR.The results confirmed the conjugation of PCL onto gelatin chains.The PCL modified gelatin can be used as biomaterials owing to their biocompatibility and biodegradation.

Self-assembly of block copolymers grafted onto a flat substrate:Recent progress in theory and simulations

Block copolymers are a class of soft matter that self-assemble to form ordered morphologies on the scale of nanome- ters, making them ideal materials for various applications. These applications directly depend on the shape and size of the self-assembled morphologies, and hence, a high degree of control over the self-assembly is desired. Grafting block copolymer chains onto a substrate to form copolymer brushes is a versatile method to fabricate functional surfaces. Such surfaces demonstrate a response to their environment, i.e., they change their surface topography in response to different external conditions. Furthermore, such surfaces may possess nanoscale patterns, which are important for some applica- tions; however, such patterns may not form with spun-cast films under the same condition. In this review, we summarize the recent progress of the self-assembly of block copolymers grafted onto a flat substrate. We mainly concentrate on the self-assembled morphologies of end-grafted AB dibloek eopolymers, junction p0int-grafted AB diblock copolymers （i.e., Y-shaped brushes）, and end-grafted ABA triblock copolymers. Special emphasis is placed on theoretical and simulation progress.

STUDY ON DYNAMIC MECHANICAL BEHAVIOUR OF POLY BUTYLACRYLATE GRAFT VINYL CHLORIDE COPOLYMERS

Dynamic mechanical behaviours of PVC ho-mopolymer. poly butylacryiate (PBA ) graft vinylchloride copolymers and blend of PVC and ACR have been investigated. The results reveal that there is semicompatible nature in the two phases in these materials,that the compatibility of the two phases decrease, -with the increase of crosslinking density of PBA backbone in graft copolyers. For different copolymer types-PB A graft copolymers had better compatibility of the two phases compared ivith the graft copolymers 晈ith core/shell backbone poly-

Block and Hetero Ethyl Cellulose Graft Copolymers Synthe- sized via Sequent and One-pot ATRP and ＂Click＂ Reactions

Ethyl cellulose graft copolymers with block and hetero side chains, ethyl cellulose graft [polystyrene-b-poly- （ethylene glycol）] [EC-g-（PS-b-PEG）] and ethyl cellulose graft polystyrene and polyethylene glycol [EC-g-（PS-PEG ）] were synthesized by atomic transfer radical polymerization （ATRP） and alkyne-azide ＂click＂ reactions and ＂one-pot＂ ATRP and ＂click＂ reactions, respectively. For the synthesis of EC-g-（PS-b-PEG）, the macroinitiator for ATRP was first synthesized via the esterification of hydroxyl groups of EC with 2-bromoisobutyryl bromide to re- sult ethyl cellulose 2-bromoisobutyryl ester （EC-Br）. The degree of substitution of bromide groups, which deter- mined the graft density, can be tailored by varying the feeding ratios of the hydroxyl groups to 2-bromoisobutyryl bromide. Then ATRP was carried out for preparing EC-g-PS-Br with well-defined length of PS chains. The EC-g-PS-Br copolymers were then converted to EC-g-PS-N3 and then reacted with end alkyne-functionalized PEG via click to result in EC-g-（PS-b-PEG）. The EC-g-（PS-PEG） copolymers were synthesized by converting bromide groups of EC-Br to azide groups （EC-Br-N3） and then by one-pot ATRP and ＂click＂ reactions. The resultant graft copolymers were characterized by FTIR and IH NMR. The results indicate the success of the synthetic procedure of the cellulose grail copolymers with block and hetero side chains.

聚丙烯/木粉复合材料的制备及性能

分别采用聚丙烯的固相接枝共聚物和熔融接枝共聚物作为聚丙烯/木粉复合材料的界面改性剂,研究两种多单体接枝共聚物用量对复合材料界面结构、拉伸性能、弯曲性能、抗冲击性能等的影响,并根据拉伸性能数据计算复合材料的界面黏结强度。结果表明:两种多单体接枝共聚物均能有效地提高复合材料的力学性能,并维持良好的热稳定性;随多单体接枝共聚物用量的增加,复合材料的力学性能提高,当多单体接枝共聚物用量为5 phr时,复合材料的界面相容性较稳定,力学性能最佳,界面黏结强度参数从2.56升至3.50以上,表明复合材料具有较强的界面黏结强度。

滴施改良剂对棉花种子萌发、幼苗生长及盐碱土结构的影响

新疆植棉区土壤盐碱化严重。为农业可持续发展提升土壤肥力进而获得棉花高产,通过盆栽试验,以南疆库尔勒盐碱化土为研究对象,研究自制天然-合成聚合物土壤改良剂对棉花种子萌芽率、发芽势、发芽指数、棉花幼苗根茎长、干鲜重的影响,并采用傅里叶变换红外光谱、扫描电子显微镜表征方法对土壤改良剂作用下土壤微观结构进行研究。研究表明,自制土壤改良剂1#即矿源黄腐酸钾-聚丙烯酸接枝盐碱土壤改良剂在3个不同浓度条件下均能改善棉花种子萌发、早期生长状况,以A2处理(880 mg土壤致良剂1#+1000 mL蒸馏水)效果最佳,相对于CK处理(1000 mL蒸馏水),发芽势和萌发率分别提高了63.2%和50.0%,幼苗鲜重增加了99.0%,干重增加了76.9%。自制土壤改良剂2#即矿源黄腐酸钾-聚丙烯酸共混盐碱土壤改良剂在低浓度下能提高种子萌发率及幼苗生物量,中高浓度有不同程度的抑制作用。改良后土壤的红外光谱变化不大,有机质吸收峰稍有增强;添加土壤改良剂能改善原始土壤致密紧实的结构,土壤颗粒之间开始团聚、土壤表面变得粗糙,改良剂1#以A2处理土壤团聚颗粒最大,颗粒间孔隙最多,改良剂2#土壤也变得相对疏松,但不同添加浓度之间变化不大。

烟炱分散型多功能黏指剂的合成与性能

以乙烯丙烯共聚物、马来酸酐、过氧化二叔丁基、防交联剂、乳化剂和胺化物为原料合成了一种多功能分散型黏度指数改进剂.考察了乙丙共聚物接枝马来酸酐过程中接枝率和凝胶率的关系,分别从反应温度、单体马来酸酐和引发剂用量等方面分析了接枝率和凝胶率的变化规律,提出了提高接枝率和降低凝胶率的方法.结果表明,在引入防交联剂的条件下,反应的接枝率和凝胶率达到了较好的平衡,分别为2.8%和3.6%.所得产品具有优异的增稠能力、烟炱分散性能、烟炱磨损性能、抗氧化性能和剪切稳定性能,兼具黏度指数改进剂和无灰分散剂的特点.

淀粉接枝丙烯酰胺与聚丙烯酰胺对高岭土动态絮凝差异的研究

高岭土等黏土矿的存在是煤泥水沉降效果差的主要原因,目前尚未有关于难沉降煤泥水动态絮凝过程的研究。相较于聚丙烯酰胺(PAM)合成单体的毒性,淀粉接枝丙烯酰胺(SAM)合成的单体可降解性好。为此,以高岭土为研究对象,系统对比了SAM与PAM对高岭土动态絮凝过程的影响。首先,考察了不同SAM与PAM用量下的沉降速度和絮凝效果。随后,通过聚焦光束反射测量(FBRM)和颗粒录影显微镜(PVM)技术研究了高岭土悬浮液在SAM和PAM作用下的不同粒级颗粒数量变化。沉降实验和FBRM-PVM测试结果表明,PAM能够形成更多的+100μm大絮团,使得PAM具有更好的沉降效果;SAM形成的絮团更稳定,对细颗粒的絮凝效果更好。最后,通过FBRM获得的数据,基于Smoluchowski模型计算了PAM和SAM作用下高岭土的絮凝动力学参数,发现PAM作用下的絮凝指数明显高于SAM,同时-30μm和30~60μm颗粒数量的动态变化主导了絮凝动力学中絮团的形成过程。总体而言,PAM可以形成更多的、松散的大絮团,有利于高岭土的快速沉降,但对微细颗粒絮凝效果不佳。相较于PAM,SAM独特的多链立体网状结构,有利于微细颗粒絮凝和形成稳定的絮团,从而避免选煤厂洗水系统中细泥的循环积聚。

水性抗氧剂组成以及含量对ASA树脂性能的影响

采用乳液聚合法制备了核壳比为6/4的ASA核壳接枝共聚物胶乳,系统地研究了水性抗氧剂的组成以及含量对ASA接枝共聚物热氧老化性能的影响,并采用熔融共混法制备ASA树脂,探究了水性抗氧剂的组成以及含量对ASA树脂力学性能、表观性能的影响。结果表明,水性抗氧剂的组成CPL/DLTP为2/3时,其ASA接枝共聚物的热氧老化性能最优;随着水性抗氧剂含量的增加,ASA接枝共聚物的氧化诱导期显著增长;水性抗氧剂的加入量超过1%以后,ASA接枝共聚物的氧化诱导期增长不显著;在230℃空气条件下,添加1%水性抗氧剂的ASA接枝共聚物的氧化诱导期可达73.1 min,其抗热氧老化能力是相同条件下不添加水性抗氧剂ASA接枝共聚物的80倍以上;水性抗氧剂的组成及含量对ASA树脂的力学性能无明显影响,对其表观性能如白度影响明显。

PE/SEBS-g-MAH/SEBS的制备及防污性能

以聚乙烯(PE)网衣为基材,苯乙烯-乙烯/丁烯-苯乙烯嵌段共聚物接枝马来酸酐(SEBS-g-MAH)和苯乙烯-乙烯/丁烯-苯乙烯嵌段聚合物(SEBS)为原料,通过浸涂法制备得到PE/SEBS-g-MAH/SEBS(PSMS);分析讨论了不同SEBS附着率时PSMS的力学性能、表面形貌、表面性质、抗蛋白吸附和抗大肠杆菌吸附等性能。结果表明,PSMS表面呈大小不一的泡孔形貌,且随着SEBS附着率的增大,PSMS表面泡孔密度增大,拉伸强度先增加后降低。当SEBS附着率为46.1%时,PSMS的拉伸强度和表面自由能分别为6.045 MPa和14.055 mN/m,抗蛋白吸附率达93.21%,同时兼具良好的抗大肠杆菌吸附性能。除此之外,PSMS在海洋挂板实验中也表现出良好的防污性能。