Syntheses and Studies of PEG-b-PNIPA Block Polymers

ＳｙｎｔｈｅｓｅｓａｎｄＳｔｕｄｉｅｓｏｆＰＥＧ┐ｂ┐ＰＮＩＰＡＢｌｏｃｋＰｏｌｙｍｅｒｓＣＡＯＷｅｉ－ｘｉａｏ＊＊ａｎｄＺＨＡＮＧＴａｏ（ＣｏｌｅｇｅｏｆＣｈｅｍｉｓｔｒｙａｎｄＭｏｌｅｃｕｌａｒＥｎｇｉｎｅｒｉｎｇ，ＰｅｋｉｎｇＵｎｉｖｅｒｓｉｔ...     

Core/shell particles containing 3-(methacryloxypropyl)-trimethoxysilane in the shell: synthesis, characterization, and application

In comparison to the corresponding single-component counterparts, core/shell particles are widely used due to their better physical and chemical properties. The surface properties of core/shell particles evidently play an important role in the process of application. It is easy to deduce that surface properties mostly depend on the properties of the component in the shell. Therefore, desirable materials of shell are very significant for the study of composite materials, especially in core/shell field. It is well known that polysiloxane has excellent properties, such as the water repellency, high flexibility, low surface energy, and biocompatibility. Its application, however, is limited due to poor cohesiveness and poor film-forming properties. Recently, much endeavor has been made to overcome such flaws. It is found that polyacrylate is commonly considered for its good cohesiveness and excellent film-forming property. The combination of polysiloxane and polyacrylate has been shown to be important in the composite material field, especially as core/shell particles. Unfortunately, their hydrophobicity is considerably different and thus, the core/shell particles consisting of polyacrylate (PA)/polysiloxane (PSi) are hard to prepare by general seeded emulsion polymerization, and are also scarcely available in the literature. In this study, the new core/shell PA/PSi particles with poly(butyl methacrylate) (PA) as the core and poly(3-(methacryloxypropyl)-trimethoxysilane) (PSi) as the shell were prepared by dispersion polymerization under the kinetically controlled conditions. The characterization of the particles by TEM, DSC, particle size analyzer as well as static contact angle confirmed the formation of core/shell structure. The application of core/shell (PA/PSi) particles also has been considered and discussed here.TEM micrographs of core/shell (PA/PSi) particles.     

苯乙烯-异戊二烯两嵌段共聚物溶液的dn/dc和紫外吸收光谱

本文研究了苯乙烯-异戊二烯两嵌段共聚物在CHCl_3中的折光指数浓度增量(dn/dc)和紫外吸收光谱。嵌段共聚物dn/dc具有很好的加和性,可以测定嵌段共聚物的组成。紫外吸收光谱的结果表明,除低苯乙烯含量的样品外,其它嵌段共聚物都显示明显的紫外增色性(UV hyperchromism)。因此UV和UV-RI双检测GPC不会得到可靠的嵌段共聚物组成数据。这种增色现象与其特征的紫外吸收谱图紧密关联     

SYNTHESIS OF BLOCK COPOLYMER FROM 5,6 -BENZO-2-METHYLENE-1,3-DIOXEPANE AND METHYL ACRYLATE VIA ATOM TRANSFER RADICAL POLYMERIZATION

Poly(methyl acrylate)-b-poly(5,6-benzo-2-methylene-1, 3-dioxepane) (PMA-b-PBMDO) was synthesized by two-step atom transfer radical polymerization (ATRP). Firstly, ATRP of methyl acrylate (MA) was realized using ethyl α-bromobutyrate (EBrB) as initiator in the presence of CuBr/2,2'-bipyridine. After isolation, poly(methyl acrylate) withterminal bromine (PMA-Br) was synthesized. Secondly, the resulting PMA-Br was used as a macromolecular initiator in theATRP of BMDO. The Structure of block copolymer was characterized by ~1H-NMR spectroscopy. Molecular weight andmolecular weight distribution were determined on a gel permeation chromatograph (GPC).     

SYNTHESES OF STYRENE-METHYL METHACRYLATE BLOCK COPOLYMER BY POLYAZOAMIDE AS INITIATOR

Polyazoamide(PAA) was used as initiator to prepare block copolymer P(MMA-b-St) byfree radical polymerization. The fraction of block copolymer was about 50%. The structureof the block-copolymer was characterized by IR and the results of ~1H-NMR and GPCshowed that the content of the block and the molecular weight (M_w) of the prepolymerand block copolymer could be controlled by varying the mol ratio of styrene/PAA andMMA/prepolymer. DSC and TEM results revealed that the block copolymer has twoseparated glass transition temperatures and phase separation within the domain structure.     

液晶聚酯与环氧嵌段共聚物的合成及表征

近年来 ,人们利用高分子液晶作为热固性环氧树脂的改性剂 ,不仅可以提高环氧树脂的韧性和强度 ,而且可以改善其热性能 ,为制备高性能的环氧树脂提供了一条新的途径[1,2 ] .目前报道所使用的液晶聚合物大多为液晶聚酯[3 ] 或液晶性聚氨酯[4] ,这些液晶聚合物与环氧树脂由于存在相容性不好的问题 ,给其实际应用带来了困难 .为了改善二者的相容性 ,本文采用溶液法合成了末端带有反应活性基团的聚酯型液晶聚合物 ,将它再与双酚Ａ环氧预聚物反应 ,制得了高分子液晶环氧嵌段共聚物 ,其合成路线如下 :2ＨＯＣＯＯＣＨ3+ ＨＯ(ＣＨ2 ) 6 ＯＨ　　Ｈ…     

Synthesis of poly[arylene ether sulfone-b-vinylidene fluoride] block copolymers

A series of α,ω-dihydroxy polyarylene sulfones (PAES) were synthesized comprising bisphenol A (PAES1, M_n=1800, 4900, and 9500 daltons), 4,4^′-biphenol (PAES2, M_n=4100 daltons), and hexafluorobisphenol A (PAES3, M_n=3300 daltons). These were reacted with α,ω-dibromo poly(vinylidene fluoride) (PVDF, M_n=1200 daltons) prepared by telomerization, to yield block copolymers possessing rigid and flexible segments. Block copolymers were characterized by FTIR, NMR, GPC, DSC, TGA and TEM. In several cases the block copolymers exhibited distinct thermal transitions, i.e. T_m and T_g for PVDF and PAES segments, respectively. Where observable, T_g of PAES domains in the block copolymers occurred at a temperature lower than the corresponding PAES homopolymer due to the flexible nature of the surrounding PVDF domains. Block copolymers exhibited a similar thermal stability to the corresponding PAES homopolymers but higher stability than the PVDF homopolymer, and much higher still than α,ω-dibromo PVDF. TEM analyses indicate that phase separation of PAES and PVDF domains occurs on the nanometer scale.     

Novel fluorinated block copolymer architectures fuelled by atom transfer radical polymerization

Block copolymers based on poly(pentafluorostyrene), PFS, in various numbers and of different lengths, and polystyrene are prepared by atom transfer radical polymerization (ATRP). Di- and triblock copolymers with varying amounts of PFS were synthesized employing either 1-phenylethylbromide or 1,4-dibromoxylene as initiators for ATRP. Diverse bromo(ester) (macro)initiators were also devised and involved in the formulation of fluorinated pentablock as well as amphiphilic triblock copolymers with a central polyether segment. Amphiphilic star-shaped fluoropolymers, hydrophobic fluorinated nanoparticles, or segmented fluorinated star-shaped block copolymers are further designed by use of different multifunctional initiators. The composition of the novel materials with PFS is determined by combination of SEC and ¹H NMR. Glass transition temperatures and thermal stabilities of the hydrophobic star-shaped PFSs on a six arm dipentaerythritol core are investigated in a wide range of molecular masses and further discussed.     

嵌段离聚物的制备及其络合和缔合性质

报道了一种氢化ＳＢＳ（ＳＥＢＳ）的化学改性方法，由此得到了一种基于ＳＥＢＳ的离聚物，其中ＰＳ嵌段接有少量羧酸盐基．用动态光散射和粘度法表征了基于ＳＥＢＳ的不同配对离子的磺酸离聚物在非极性溶剂中的缔合行为，给出了缔合物存在的证据和缔合物尺寸的定量数据．ＳＥＢＳ磺酸盐离聚物与含吡啶基的无规共聚物在稀溶液和本体中能形成分子间的络合物，这从共混物溶液粘度的反常增大和本体Ｔｇ的显著增加得到了证明．用粘度法、透射电子显微镜表征和证实了ＳＥＢＳ羧酸钠离聚物在水中可以形成稳定的胶体分散．疏水粒子为表面的离子基团所稳定．     

Comportement tensioactif des copolymères amphiphiles a séquence hydrophile polyélectrolyte

Résumé La courbe représentant, en fonction de la concentrationc, la tension interfaciale entre le toluène et une solution aqueuse d'un copolymère á blocs amphiphile á séquence hydrophile polyélectrolyte (polystyrène-b-polyvinyl-2-pyridine quaternisée au bromure d'éthyle) est foncièrement différente de celle que l'on obtient avec les détergents classiques.Les longues séquences polyélectrolytes ancrées á l'interface y établissent entre les deux phases une différence de potentiel électrique bien supérieure á celle que l'on obtient avec les détergents classiques. Il en résulte que le système reste éloigné de l'équilibre thermodynamique. Comme les énergies d'activation des processus d'adsorption et de désorption sont de nature différente, les courbes (,c) etablies en concentration croissante et décroissante sont non seulement distinctes, mais de caractères différents.

---

Summary Plotting the water toluene interface tension against the concentrationc, one gets quite different behaviours using classical detergents (Sodium laurylsulfate) or ampholytic block copolymers with polyelectrolytic hydrophilic sequence. (polystyrene-b-polyvinyl-2-pyridine quaternized with ethylbromid).These polyelectrolytic sequences build at the interface a much larger electric potential drop than usual detergents do. It follows that the system keeps far away from the thermodynamic equilibrium. Since adsorption and desorption processes have activation energies of different natures, it turns out that the (,c) curves are quite different in characters if constructed in growing or fallingc values.

---

Zusammenfassung Kurven, welche die Wasser-Toluol-Grenzflächenspannung als Funktion der Konzentrationc wiedergeben, sind für gewöhnliche Tenside und für Ampholytblock-Copolymere mit einer polyelektrolytartigen Sequenz, völlig verschiedenDie polyelektrolytartige Sequenz bildet an der Grenzfläche einen weitaus größeren elektrischen Potentialsprung als gewöhnliche Tenside. Daraus folgt, daß man dem thermodynamischen Gleichgewicht fern bleibt, und, da Ad- und Desorptionsprozesse unterschiedliche Aktivationsenergien besitzen, sind die (,c) Kurven mit steigenden und fallendenc-Werten völlig verschieden.