Studies on microstructure and aqueous solution properties of block copolymer of acrylamide-styrene

Three series of block copolymers of acrylamide (AM) and styrene (St) as hydrophobic comonomer with varied microstructures were prepared in microemulsion medium by changing feed ratio of monomers, ratio of St to surfactant, and amount of initiator, respectively. The effects of microstructure factors of the amphiphilic block copolymers PAM-b-PSt on their aqueous solution properties were investigated by fluorescence probe technique and surface tension measurement in detail. The experimental results show that the aqueous solution properties of PAM-b-PSt are strongly dependent on their microstructure factors, such as the length and content of PSt hydrophobic blocks in the copolymers and their molecular weight. It was found that the main microstructure factors which effect the hydrophobic association behavior of the copolymer PAM-b-PSt are the length and content of PSt hydrophobic blocks in the copolymer, whereas the hydrophobic association behavior of the copolymer is not affected nearly so much by molecular weight in more dilute regions. At the same time, it was also found that the main microstructure factors which affect the surface activity of the copolymer are the content of PSt hydrophobic blocks in the copolymer and molecular weight, whereas the length of PSt blocks in copolymer does not affect surface activity of the copolymer nearly so much under fixed content of PSt hydrophobic blocks and molecular weight in the copolymer.     

丙烯酰胺-苯乙烯双亲嵌段共聚物的微结构及水溶液行为

通过改变丙烯酰胺(AM)与苯乙烯(St)的投料比、苯乙烯与表面活性剂的加入量之比及引发剂加入量,在微乳液中制备了分子链微结构系列变化的丙烯酰胺-苯乙烯双亲嵌段共聚物(PAM-b-PSt),用荧光探针法与表面活性测定法详细地研究了共聚物中PSt嵌段长度、含量及分子量等微结构因素对共聚物在水溶液中的疏水缔合性与表面活性的影响.结果表明,当共聚物水溶液的浓度高于临界缔合浓度时,PAM-b-PSt的疏水缔合作用以分子间的缔合为主.若共聚物中PSt嵌段含量及分子链长一定时,随着PSt疏水嵌段长度增长,PAM-b-PSt的疏水缔合性增强,而对共聚物的表面活性影响很小.若共聚物中PSt疏水嵌段长度及分子链长一定时,PAM-b-PSt的疏水缔合性随着PSt嵌段含量的变化而变化,当PSt嵌段含量一定时,使大分子链之间产生最强的疏水缔合作用;而其表面活性则随着PSt嵌段含量的增大而增强.若共聚物中PSt疏水嵌段长度及含量一定时,分子量对其表面活性有较大的影响,分子量越高,表面活性越差;同时,在较稀的溶液浓度范围内,分子量对PAM-b-PSt的疏水缔合性的影响则很小.     

Cyclodextrin gels which have a temperature responsiveness

β-Cyclodextrin (CD) gels crosslinked by epichlorohydrin (CD-gel) were modified with poly(N-isopropylacrylamide) (PIPA; M_n 4900) chains. The CD residue in the gel associated with 8-anilino-1-naphthalenesulfonic acid (ANS) more strongly than the free PIPA-carrying CD. The van't Hoff plot for complexation of ANS with the gel drifted largely from linear relationship above the coil-globule transition temperature of individual PIPA chains. Furthermore, a relatively more significant temperature effect on the stereoselective adsorption of phenylalanine to the CD gel was observed by the modification with PIPA chains. These results imply that the ability of the CD-gel–PIPA conjugate to form inclusion complex could be skillfully controlled by temperature. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1535–1541, 1997     

丙烯酰胺-苯乙烯双亲嵌段共聚物水溶液的表面活性及增溶性

在微乳液介质中制备了系列的丙烯酰胺 (AM)与苯乙烯 (St)的双亲嵌段共聚物 (PAM b PSt) ,用紫外分光光度法测定了共聚物的组成 ,用乌氏粘度计测定了共聚物的特性粘数 [η],并用其相对表征共聚物的分子量大小 .重点研究了双亲嵌段共聚物 (PAM b PSt)疏水链段在水溶液中的缔合行为、共聚物的表面活性及其对有机物的增溶性能 ,考察了共聚物分子组成 (疏水链段含量 )与分子量对其表面活性与增溶性能的影响规律 .研究结果表明 ,由于疏水链段的憎水性 ,PAM b PSt的分子链在水溶液表面会形成表面吸附 ,从而降低水溶液的表面张力 ;而在水溶液中 ,在疏水相互作用下 ,PAM b PSt分子链中的苯乙烯疏水链段会形成分子间或分子内的胶束 ,烃类有机物可增溶其中 ;疏水链段含量越大 ,分子量越小 ,PAM b PSt的表面活性与增溶性能越强     

PSt-b-PEO增容PA6/PS共混体系的研究

采用动态力学方法（ＤＭＡ），形态学方法（ＳＥＭ），研究了ＰＳｔ ｂ ＰＥＯ存在下尼龙６（ＰＡ６）／聚苯乙烯（ＰＳ）共混体系的相容性．研究表明，ＰＡ６和ＰＳ的简单共混体系，分散相相畴尺寸大，相界面清晰，断裂面光滑，呈脆性断裂，相容性极差，属不相容体系．而加入少量ＰＳｔ ｂ ＰＥＯ后分散相尺寸变小，界面层变厚，界面粘结力增强，表现出韧性特征．     

Polyisobutylene-containing block polymers by sequential monomer addition. II. Polystyrene–polyisobutylene–polystyrene triblock polymers: Synthesis,characterization, and physical properties

New linear and three-arm star thermoplastic elastomers (TPEs) comprising a rubbery polysobutylene (PIB) midblock flanked by glass polystyrene (PSt) blocks have been synthesized by living carbocationic polymerization in the presence of select additives by sequential monomer addition. First, isobutylene (IB) was polymerized by bi- and trifunctional tert-ether (dicumyl- and tricumyl methoxy) initiators in conjunction with TiCl₄ conintiator in CH₃Cl/methylcyclohexane (MeCHx) (40/60 v/v) solvent mixtures at ?80°C. After the living, narrow molecular weight, distribution PIB (M?_w/M?_n = 1.1-1.2) has reached the desired molecular weight, styrene (St) together with an electron pair donor (ED) and a proton trap (di-tert-butylpyridine, DtBP) were added to block PSt from the living chain ends. Uncontrolled initiation by protic impurities that produces PSt contamination is prevented by the use of DtBP. PSt-PIB-PSt blocks obtained in the absence of additives are contaminated by homopolymer and /or diblocks due to inefficient blocking and initiation by protic impurities, and exhibit poor physical properties. In contrast in the presence of the strong ED N,N-dimethylacetamide (DMA) and DtBP the blocking of St from living PIB chain occurs efficiently and block copolymers exhibiting good mechanical properties can be prepared. Virgin TPEs can be repeatedly compression molded without deterioration of physical properties. The products exhibit a low and a high temperature T_g characteristic of phase separated PIB and PSt domains. Transmission electron microscopy of linear triblocks containing ～ 34 wt % PSt also indicates microphase separation and suggests PSt rods dispersed in a PIB matrix.     

Telomerization of styrene with bromotrichloromethane

The photo-initiated reactions between styrene and bromotrichloromethane have been studied at 30. The analysis of the telomer products by gel permeation chromatography has been refined since the previously published work; the relative proportions of several smaller telomers have been estimated. The results show a considerable increase in the magnitude of the transfer constant over the first few propagation steps of the reaction, with a limiting value after the incorporation of three monomer units into the growing polymer radical.     

Staged Surface Patterning and Self‐Assembly of Nanoparticles Functionalized with End‐Grafted Block Copolymer Ligands

Using two orthogonal external stimuli, programmable staged surface patterning and self‐assembly of inorganic nanoparticles (NPs) was achieved. For gold NPs capped with end‐grafted poly(styrene‐block‐(4‐vinylbenzoic acid)), P(St‐block‐4VBA), block copolymer ligands, surface‐pinned micelles (patches) formed from NP‐adjacent PSt blocks under reduced solvency conditions (Stimulus 1); solvated NP‐remote P(4VBA) blocks stabilized the NPs against aggregation. Subsequent self‐assembly of patchy NPs was triggered by crosslinking the P(4VBA) blocks with copper(II) ions (Stimulus 2). Block copolymer ligand design has a strong effect on NP self‐assembly. Small, well‐defined clusters assembled from NPs functionalized with ligands with a short P(4VBA) block, while NPs tethered with ligands with a long P(4VBA) block formed large irregularly shaped assemblies. This approach is promising for high‐yield fabrication of colloidal molecules and their assemblies with structural and functional complexity.     

原子转移自由基聚合制备聚(甲基丙烯酸甲酯-b-苯乙烯)时单体聚合顺序对嵌段效率的影响

采用原子转移自由基聚合研究了聚（ 甲基丙烯酸甲酯 ｂ 苯乙烯） 嵌段共聚物的合成,实验结果表明,当先进行甲基丙烯酸甲酯的聚合,然后再进行苯乙烯的聚合时,得到了完全的嵌段共聚物;反之,如果改变单体的聚合顺序,则嵌段效率很低．用聚合物末端Ｃ—Ｘ（Ｘ＝ Ｃｌ,Ｂｒ） 键的断裂能对实验结果进行了解释．     

Compatabilization of polystyrene/polypropylene blends by styrene–butadiene block copolymers with differing polystyrene block lengths

Compatibilization of polystyrene/polypropylene (PS/PP) blends, by use of a series of butadiene–styrene block copolymers was studied by means of small‐angle X‐ray scattering (SAXS) and transmission electron microscopy (TEM). The compatibilizers used differ in molar mass and the number of blocks. It was shown that the ability of a block copolymer (BC) to participate in the formation of an interfacial layer (and hence in compatibilization) is closely associated with the molar mass of styrene blocks. If the styrene blocks are long enough to form entanglements with the styrene homopolymer in the melt, then the BC is trapped inside this phase of the PS/PP blends, and its migration to the PS/PP interface is difficult. In this case, the BC does not participate in the formation of the interfacial layer nor, consequently, in the compatibilization process. On the other hand, the BC's with the molar mass of the PS blocks below the critical value are proved to be localized at the PS/PP interface. This preferable entrapping of some styrene–butadiene BC's in the PS phase of the PS/PP blend is, of course, connected to the differing miscibility of the BC blocks with corresponding components of this blend. Although the styrene block is chemically identical to the styrene homopolymer in the blend, the butadiene block is similar to the PP phase. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1647–1656, 1999     

PSt种子与“花瓣”形PSt/PAN复合颗粒的制备

以过硫酸钾为引发剂,在乙醇/水的混合介质中使苯乙烯进行无皂乳液聚合,得到了单分散亚微米级聚苯乙烯(PSt)微球.用扫描电子显微镜研究了引发剂浓度、单体浓度、反应温度和溶剂组成对PSt微球粒径的影响.结果表明,改变上述条件能明显影响其粒径.以所得单分散聚苯乙烯微球为种子,在丙烯酸单封端聚乙二醇大分子单体存在的条件下,使丙烯腈和少量苯乙烯进行新的无皂种子乳液聚合,在合适的条件下制得到了“花瓣”形的聚合物复合颗粒,为深入探讨这类特殊形态聚合物颗粒的形成机理提供了新的佐证.     

Monitoring the transformation of colloidal crystals by styrene vapor using atomic force microscopy

The stages of transformation of a colloidal crystalline film of latex spheres to a new periodic structure were imaged by atomic force microscopy. Colloidal crystalline films were prepared with 320 nm diameter poly(styrene-co-2-hydroxyethyl methacrylate) (PSt/HEMA) spheres. The hexagonally ordered surfaces of the colloidal crystalline films were transformed with styrene vapor at room temperature to a new morphology having holes in the surface and the same periodicity as the original films. The surfaces of colloidal crystals and the transformed films have a raspberry-like texture superposed on the 320 nm hexagonal periodicity. Both height images and phase images reveal that the latex spheres shrink and the transformation proceeds by an order-disorder-order sequence. The final structure is an interconnected colloidal array with smaller polystyrene particles dispersed in a continuous PSt/HEMA matrix.     

Preparation of organic/inorganic hybrid and hollow particles by catalytic deposition of silica onto core/shell heterocoagulates modified with poly[2-(N,N-dimethylamino)ethyl methacrylate

The organic/inorganic hybrid particles PSt/P(St-CPEM)(θ)-g-PDMAEMA/SiO(2) were prepared by catalytic hydrolysis and subsequent polycondensation of tetraethoxysilane in the poly[2-(N,N-dimethylamino)ethyl methacrylate] (PDMAEMA) layers grafted on the PSt/P(St-CPEM)(θ) core/shell heterocoagulates. The micron-sized PSt core and the submicron-sized P(St-CPEM) shell particles bearing ATRP initiating groups were synthesized by dispersion polymerization of styrene (St) and emulsifier-free emulsion polymerization of St with 2-chloropropionyloxyethyl methacrylate (CPEM), respectively. The raspberry-shaped PSt/P(St-CPEM)(θ) heterocoagulates with a controlled surface coverage (θ=0.51, 0.81) were prepared by hydrophobic coagulation between the core and the shell particles in an aqueous NaCl solution near the T(g) of P(St-CPEM). Surface modification of heterocoagulates was carried out by ATRP of DMAEMA from the shell particles adsorbed on the core particles. Silica deposition was performed by simply adding tetraethoxysilane to a water/methanol dispersion of PSt/P(St-CPEM)(θ)-g-PDMAEMA. The SEM and TGA revealed that the resulting PSt/P(St-CPEM)(θ)-g-PDMAEMA/SiO(2) composites maintain a raspberry-like morphology after deposition of silica onto the PDMAEMA layer grafted on heterocoagulates. The micron-sized, raspberry-shaped or the submicron-sized, hole-structured silica hollow particles were obtained selectively by thermal decomposition of the PSt/P(St-CPEM)(θ)-g-PDMAEMA/SiO(2). The oriented particle array was fabricated by dropping anisotropically perforated silica particles onto a glass substrate settled at the bottom of a bottle filled with chloroform.     

水溶性聚合物和两亲聚合物 16.聚苯乙烯/聚丙烯酰胺嵌段聚合物的合成和表征

采用聚偶氮酯引发剂,合成了聚苯乙烯/聚丙烯酰胺嵌段聚合物(PSt/PAM)。考察了含偶氮基聚苯乙烯预聚物(pre-PSt)在1,4-二氧六环中引发AM的聚合反应行为,讨论了影响第二单体转化率和聚苯乙烯均聚物含量的因素。用元素分析、溶解性、红外光谱、DSC、TG和裂解色谱表征了PSt/PAM嵌段聚合物。     

聚苯乙烯-b-聚硅氧烷-b-聚苯乙烯三嵌段共聚物的合成及表征

采用乙烯基封端的聚 (二甲基硅氧烷 )与溴化氢反应制得末端含有C Br的双官能聚 (二甲基硅氧烷 ) ,以此聚 (二甲基硅氧烷 )大分子为引发剂 ,CuCl为催化剂 ,4 ,4′ 二 (5 壬基 ) 2 ,2′ 联吡啶为配体 ,通过原子转移自由基聚合法 ,制得分子量和结构可控的聚苯乙烯 b 聚硅氧烷 b 聚苯乙烯 (PSt b PDMS b PSt)共聚物 .     

Adsorption of cationic polyelectrolyte at the solid/liquid interface and dispersion of nanosized silica in water

Adsorption of cationic polyelectrolyte, a homopolymer of maleimide propyl trimethylammonium chloride (MPTMAC), on silica nanoparticles from aqueous solution was studied. The adsorbed amount of MPTMAC and the adsorption layer thickness from solutions of different pH, polyelectrolyte concentration, salt type, and salt concentration were measured. The adsorbed amount exhibited a maximum as a function of the electrolyte concentration. The onset of the decline in the adsorbed amount depended on the type of counterions. The thickness of the adsorption layer increased gradually with increased of electrolyte concentration and leveled off at high electrolyte concentration. The enhanced adsorption in the presence of Na2SO4 can be explained by the bivalent SO4(2-) causing a better shielding effect. With increasing pH the adsorbed amount of MPTMAC increased, whereas the thickness of an adsorbed layer of MPTMAC decreased. At low polyelectrolyte concentrations unstable silica suspensions were observed from a stability test. At high polyelectrolyte concentrations the higher particle coverage caused electrosteric stabilization of the dispersion. However, further increase in MPTMAC concentration after saturated adsorption would flocculate the dispersed system. At low pH, MPTMAC tending to create a loops or tails conformation stabilized the suspension.     

Viscometric study of the coil-globule transition of poly(N-isopropylacrylamide) in solutions of surfactant

The coil-globule transition of poly(N-isopropylacrylamide) (systematic name: poly-[1-(isopropylaminocarbonyl)ethylene]) has been viscometrically investigated in low-concentration aqueous sodium dodecyl sulfate solution. In this environment, even if the macromolecular coils collapse as the temperature increases above the lower critical solution temperature of the polymer, 34°C, the polymer does not precipitate. It seems that the hydrophobically collapsed macromolecular coils do not aggregate, but remain in solution with the aid of surface charges supplied by surfactant ions adsorbed through hydrophobic interactions.     

Self-organization of dipeptide-grafted polymeric nanoparticles film: A novel method for surface modification

Novel dipeptide-grafted polymeric nanoparticles were prepared by grafting the dipeptide (Gly-Gly) to a block copolymer backbone, comprised of styrene-alt-(maleic anhydride) and styrene. In aqueous solution PSt₁₃₀-b-P(St-alt-MAn)₅₈-g-GlyGly₂₆ formed stable dispersed spherical aggregates of ca. 75 nm. The critical micelle concentration for the dipeptide-grafted block copolymer self-aggregates was 6.3 × 10⁻³ mg mL⁻¹. The zeta-potential of the aggregates was estimated experimentally. The dispersed polymer nanoparticles effectively self-organized to form stable nanoparticle thin films on hydrophobic solid surfaces, such as octadecyltrichlorosilane modified glass (OTS-G). As the ionic strength and temperature of the polymer suspension increased the surface coverage of the nanoparticle film increased and its hydrophobicity (water contact angle) decreased. Significantly less bovine serum albumin (BSA) adsorbed to nanoparticles modified surfaces with compared OTS-G surfaces. Diglycine grafted polymer nanoparticles have the potential to be used as a novel platform to study protein-protein interactions and to control fouling.     

ABA型两亲嵌段共聚物的合成及表征

以α ,α′ 二溴代二甲苯为引发剂 ,CuBr/2 ,2′ 联吡啶为催化体系 ,制备了双溴端基的分子量分布窄的聚苯乙烯 (MWD =1 18) .再以此作为大分子引发剂 ,实现了甲基丙烯酸对硝基苯酯的原子转移自由基聚合 ,制得了分子量可控且分子量分布窄的ABA型嵌段共聚物 ,再经水解、酸化 ,得到了聚甲基丙烯酸 b 聚苯乙烯 b 聚甲基丙烯酸ABA型两亲嵌段共聚物     

UV-Vis and Surface Photovoltage Spectra of Fe2O3/Polystyrene Composite Microspheres

IntroductionIn recentyears,there has been a general inter-est in the encapsulation of inorganic particles withorganic polymers[1] . This kind of composite parti-cles consists of an inorganic core and a polymershell[2 ] .The aim of the encapsulation is to improvethe physical properties of products,and to meetthe development of new materials having a highfunctionality in the fields such as biology,medicine,pharmacology and electronics etc.[3 ,4 ] .The encapsulation of oxide nanoparticles witha p…