Aggregation behavior of polypropylene oxide with electric charges at both ends in aqueous solution

The aggregation behavior of polypropylene oxide (PPO) with positive charges at both ends was investigated in aqueous solution by means of the measurements of solution turbidity, dynamic light-scattering, differential scanning calorimetry, and dye solubilization. The positive charges were produced by protonation of terminal NH(2) groups attached to the polymer composed of 33 PO units. It was found that the aggregation behavior is quite sensitive to temperature. At low temperature, the polymer dissolves in water as a unimer. When temperature is increased, the unimer solution undergoes a phase separation to give a turbid solution. Further increase in temperature produces a transparent micellar solution. The aggregation of the polymer molecules must be induced by the dehydration of PPO chain caused by temperature increase. According to the analysis of heat absorptions associated with the melting of the solid mixture and the phase separation of the unimer solution, it is suggested that approximately 10% dehydration of PPO chain causes the phase separation. The temperature-composition phase diagram of aqueous mixture of this polymer was constructed on the basis of turbidity and DSC experiments, which reveals the aggregation behavior of this polymer in aqueous medium as a function of concentration and temperature.     

二元阴离子型丙烯酰胺共聚物在二价金属离子存在下相分离行为的研究

水溶性丙烯酰胺类共聚物 ,作为粘度改性剂 ,在工业上已得到广泛应用 .特别近年来 ,它们大量应用于石油工业强化采油技术 ,引起了人们很大的重视[1] .目前 ,这类用途的聚合物 ,主要在聚丙烯酰胺结构中 ,引入阴离子组分和不断增高产物分子量的方法 ,以提高聚合物溶液粘度和增粘效果 ,然而 ,在二价金属离子 (如Ｃａ2 + ,Ｍｇ2 + 等 )存在下 ,羧酸阴离子型丙烯酰胺类共聚物很容易络合发生沉淀 ,从而失去增粘作用[2 ] .同时这类聚合物中酰胺基不稳定 ,易发生水解反应转化为羧酸基 ,并随温度升高而加剧[3 ] ,因此在温度较高的应用条件下 ,二价金属…     

Aggregation of poly(1,3‐cyclohexadiene): Effects of molecular weight and polymer chain structure

The aggregation of poly(1,3‐cyclohexadiene) (PCHD), obtained by anionic polymerization with alkyllithium/amine systems, was examined using size exclusion chromatography (SEC) and size exclusion chromatography coupled with a multiangle laser light scattering photometer (SEC‐MALS). The PCHD polymer chain has a structure consisting of a main chain formed by 1,2‐addition (the 1,2‐CHD unit) and 1,4‐addition (the 1,4‐CHD unit). Mild stirring with relatively low temperature in the polymerization reaction forms an aggregation of PCHD. The molecular weight and molar ratio of 1,2‐CHD/1,4‐CHD units in the polymer chain strongly influence the aggregation of PCHD. In a high molecular weight PCHD, containing ～50% 1,2‐CHD units, an aggregation of the polymer was observed in tetrahydrofuran (THF) solution at room temperature. This aggregation of PCHD was soluble in 1,2,4‐trichlorobenzene (TCBz) and could be separated into each polymer molecule. In contrast, a polymer chain with a high content of 1,4‐CHD units having a relatively low cis‐stereospecificity was easily soluble in THF and TCBz without aggregating. A long polymer chain structure with a high content of 1,2‐CHD units is considered to be the reason for the generation of strong intermolecular forces contributing to the aggregation of PCHD with the solvophobic interactions. The degree of aggregation could be controlled by the conditions of the PCHD polymer solution. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1442–1452, 2006     

Solution properties of thermothickening copolymers bearing hydrocarbon end‐capped oxyethylene units

Novel thermothickening copolymers composed of acrylamide and a macromer bearing hydrocarbon end‐capped oxyethylene units were synthesized. Influences of polymer concentration, salt content, shear rate, and temperature on the solution behavior were investigated. The polymer solution exhibited shear‐thickening behavior at low‐to‐moderate shear rates (<50 s^?1), and the shear‐thickening behavior was dependent on polymer concentration, NaCl content, and temperature. With the increase of salinity, apparent viscosity of polymer solution increased dramatically (especially at low shear rates). At higher NaCl content (>20 wt %), polymer solutions became physical gel, and the apparent viscosity increased by several orders of magnitude. The polymer solutions exhibited excellent thermothickening behavior, even at the low concentration of 0.15 wt %. The results of rheological measurements showed that the storage and loss modulus were successfully fitted to a single Maxwell element at low temperature (<60 °C). © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1799–1808, 2010     

电化学聚合漆酚钴膜配位结构与催化性能研究

电化学方法合成的聚合漆酚 (EPU)通过与氯化钴的异丙醇溶液作用 ,生成聚合漆酚钴配合物膜(EPU Co3+ ) .采用红外光谱、XPS光电子能谱、DTA TG、动态机械热分析 (DMTA)以及原子发射光谱 (AES)等手段进行表征 ,确定其配位结构 ,即每个钴离子与EPU中两个链节单元的羟基发生配位而交联 ,因此玻璃化转变温度和耐热性能均得到提高 .实验表明 ,此配合物膜在室温下的Na2 SO3水体系 (pH =7)中能催化引发VAc的聚合     

New silicon-containing heterocyclic polyimides

New aromatic polyimides and polyamide-imides with phenylquinoxaline rings and dimethylsilane units have been synthesized by solution polycondensation reaction of aromatic diamines containing phenylquinoxaline units with bis(3,4-dicarboxyphenyl)-dimethylsilane dianhydride, or with a diacid chloride resulting from the reaction of this dianhydride with p-aminobenzoic acid. These polymers were easily soluble in organic solvents, such as N-methylpyrrolidinone and dimethylacetamide, and showed high thermal stability with decomposition temperature being above 440°C and glass transition temperature in the range of 245-285°C. Very thin coatings were deposited from polymer solutions onto silicon wafers and exhibited smooth, pinhole-free surface in atomic force microscopy investigations. Some of these polymers showed blue fluorescence in solution and films, with a maximum in the range of 415-425 nm.     

Aggregation behavior of polypropylene oxide end-capped by positive charges

We investigated the aggregation behavior of poly(propylene oxide) with positive charges at both ends in aqueous solution by means of solution turbidity, dynamic light-scattering, solubilization of fluorescence probe, and optical microscopic observation. The positive charges were produced by protonation of terminal NH2 groups attached to the polymer composed of 33 PO units. It was found that the polymer exists as unimers at low temperature and as micelles at high temperature, whereas at intermediate temperature, there appear different aggregation states depending on the polymer concentration; i.e., 100-nm size aggregates which might be vesicles, 1-microm size particles (oil droplets), and a certain turbid phase showing a characteristic texture under optical microscopic observation. Filtration experiments to remove the oil droplets showed that the insoluble components with less hydrophilic property included in the polymer sample are responsible for the formation of oil droplets. Comparison of the phase diagrams obtained for the polymer/H2O mixtures before and after the filtration treatment suggests that the formation of 100 nm size aggregates and some unidentified phase in between unimer and micellar regions is an intrinsic property of the poly(propyrene oxide) chain end-capped by electrical charges.     

Aqueous solutions of amphiphilic polysaccharides: Concentration and temperature effect on viscosity

Amphiphilic polymers have been prepared by chemical modification of a neutral bacterial polysaccharide, dextran, consisting of α-1,6 linked glucose units. Various amounts of aliphatic hydrocarbon groups with six carbon atoms are attached along the dextran chains by ether links. The viscosities of their aqueous solutions in the dilute domain and in the beginning of the semi-dilute domain are considered with particular interest for the variation with temperature and polymer concentration.The equations of Fedors and Martin are shown to conveniently depict the effect of polymer concentration over the whole investigated range. A semi-empirical equation is established between the critical concentration deduced from Fedors equation and both the Huggins coefficient and the intrinsic viscosity (parameters deduced from the results in the dilute domain).The variation of solution viscosity with temperature is also examined. Andrade equation, combined with Martin or Fedors equation, is shown to account for the temperature effect. Particularly, the variation of the activation energy with polymer concentration is conveniently depicted. The validity of the derived semi-empirical equations is extended to other polymer solutions using literature data.     

Molecular mobility of spin-labelled terephthaloyl chloride and 1,10-decanediol copolymer in solution

Intramolecular mobility of spin-labelled terephthaloyl chloride and 1,10-decanediol copolymer in solution was investigated using a polymer in which the label was rigidly attached to the main chain methylene groups. Correlation times and effective segmental dimensions were measured, as were the frequency and amplitude of the high-frequency torsional vibrations of the main chain monomer units. The amplitude of high-frequency torsional vibrations was shown to increase with increasing temperature.     

A viscosity self-oscillation of polymer solution induced by the Belousov-Zhabotinsky reaction under acid-free condition

We succeeded in measuring a viscosity self-oscillation induced by the Belousov-Zhabotinsky (BZ) reaction for a polymer solution on the constant temperature condition under acid-free condition. The polymer chain is consisted of N-isopropylacrylamide, ruthenium complex as a catalyst of the BZ reaction, and an acrylamide-2-methylpropanesulfonic acid (AMPS) as a pH and the solubility control site. The viscosity self-oscillation for the AMPS-containing polymer solution was attributed to the difference between viscosities for the polymer solution in the reduced and oxidized states. The effects of the polymer concentration and the temperature of the polymer solution on the viscosity self-oscillation were investigated. As a result, the viscosity self-oscillating behavior significantly depended on the polymer concentration and the temperature of the polymer solution. The period of the viscosity self-oscillation decreased with increasing temperature in accordance with the Arrenius equation.     

Transition from Incomplete to Complete Wetting of Solid Surface in Polymer–Solvent System: 2. The Regime of Strong Adsorption

The transition from incomplete to complete wetting of the solid surface by a semidilute polymer solution coexisting at equilibrium with the very-dilute polymer solution was studied using the Canh–de Gennes theory under the conditions corresponding to the tricritical state of semidilute solution and strong adsorption of the chain units on a substrate. It was established that the wetting transition can occur as the first- or second-order phase transition or as the transition of tricritical wetting depending on the repulsion energy of segments that are on the substrate surface. Near the temperatures of these transitions, the character of the variations in the differences of surface concentrations that are established at the boundaries of the substrate with semidilute and dilute polymer solutions, as well as in the differences of interfacial tensions and the cosine of contact angle were determined. It was shown that the temperature of each of these phase transitions varies in proportion to the surface potential of the substrate and does not depend on the polymer molecular mass. The observed behavior differs essentially from that established near the critical point of a polymer–solvent system.     

含X-型和棒型两种液晶基元的主链型系列芳族共聚酯的研究

 采用含X-型和棒型液晶基元的两种不同单体,通过改变X-型液晶基元单体的结构和柔性链段长度,经高温溶液缩聚,合成了一系列主链型共聚液晶高分子.研究发现,所有样品都具有很好的热致液晶性及宽广的液晶态温度范围.随单体结构改变,共聚物的相转变温度大致呈规律性变化.     

含X-型和棒型两种液晶基元的主链型系列芳族共聚酯的研究

采用含X-型和棒型液晶基元的两种不同单体,通过改变X-型液晶基元单体的结构和柔性链段长度,经高温溶液缩聚,合成了一系列主链型共聚液晶高分子.研究发现,所有样品都具有很好的热致液晶性及宽广的液晶态温度范围.随单体结构改变,共聚物的相转变温度大致呈规律性变化.     

电化学聚合漆酚钴膜引发甲基丙烯酸甲酯（MMA）聚合的研究

利用电化学技术合成的聚合漆酚（EPU）与氯化钴的异丙醇溶液反应,得到电化学聚合漆酚钴配合物膜,经XPS光电子能谱、红外光谱、TG－DTA、动态机械热分析（DMTA）以及原子发射光谱（AES）等手段进行表征并确定其结构。由于每个钴离子与EPU分子中两个链节单元的羟基发生配位引进进一步交联。因此玻璃化转变温度和耐热性能均得到提高。实验表明,在常温下的Na2SO3水体系（pH值为7）中配合物膜能引发甲基丙烯酸甲酯（MMA）聚合。     

电化学聚合漆酚钐配合物的研究

利用电化学方法合成的聚合漆酚 (EPU)与氯化钐的异丙醇溶液作用 ,得到聚合漆酚钐配合物 (EPU Sm3 + ) .采用红外光谱、紫外 可见光光谱、荧光光谱、XPS光电子能谱、动态机械热分析 (DMTA)以及差热 热重(DTA TG)等手段进行表征 ,确定其每个钐离子与EPU分子中三个链节单元的羟基发生配位 .原子发射光谱(AES)结果确定钐含量达 13 18% .配合物的电阻为 9 6× 10 1 0 Ω(EPU为 7 9× 10 1 0 Ω) .发现因配位作用而使配合物进一步交联 ,而难溶于有机溶剂 ,同时玻璃化转变温度和耐热性能得到提高     

Soluble complexes in aqueous mixtures of low charge density comb polyelectrolyte and oppositely charged surfactant probed by scattering and NMR

A low charge density polyelectrolyte with a high graft density of 45 units long poly(ethylene oxide) side-chains has been synthesized. In this comb polymer, denoted PEO(45)MEMA:METAC-2, 2 mol% of the repeating methacrylate units in the polymer backbone carry a permanent positive charge and the remaining 98 mol% a 45 unit long PEO side-chain. Here we describe the solution conformation of this polymer and its association with an anionic surfactant, sodium dodecylsulfate, SDS. It will be shown that the polymer can be viewed as a stiff rod with a cross-section radius of gyration of 29 A. The cross section of the rod contracts with increasing temperature due to decreased solvency of the PEO side-chains. The anionic surfactant associates to a significant degree with PEO(45)MEMA:METAC-2 to form soluble complexes at all stoichiometries. A cooperative association is observed as the free SDS concentration approaches 7 mM. At saturation the number of SDS molecules associated with the polymer amounts to 10 for each PEO side-chain. Two distinct populations of associated surfactants are observed, one is suggested to be molecularly distributed over the comb polymer and the other constitutes small micellar-like structures at the periphery of the aggregate. These conclusions are reached based on results from small-angle neutron scattering, static light scattering, NMR, and surface tension measurements.     

New environmentally responsive fluorescent N‐isopropylacrylamide copolymer and its application to DNA sensing

We report two novel multifunctional copolymers consisting of a temperature‐responsive poly(N‐isopropylacrylamide) (PNIPAA) segment and a fluorescent fluorene‐containing acrylic polymer segment with pH responsiveness and/or DNA‐sensing ability. The functional acrylic monomer with a fluorene dimer side group substituted with amino units was synthesized first. Then, it was copolymerized with N‐isopropylacrylamide to result in a new water‐soluble, fluorescent PNIPAA copolymer ( P1 ). The fluorescent properties of P1 under neutral and acidic conditions did not change with the temperature. However, significant variation was observed under basic conditions. The protonation of the amino moiety at a low pH improved the solubility and prevented aggregation for fluorescence quenching, but not under the basic conditions. Although aggregation of the fluorene units was significant at room temperature under basic conditions, the aggregation was resolved at a temperature above the lower critical solution temperature. These findings indicated the pH‐ and temperature‐responsive characteristics of P1 . Moreover, after the amino groups were quaternized, the obtained polymer could be used as a biosensor because the fluorescence intensity was quenched with the addition of DNA. This study demonstrates that multifunctional materials with pH‐ and temperature‐sensing characteristics and biological molecules could be realized by the incorporation of a functional fluorene‐containing moiety with PNIPAA. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5495–5504, 2006     

Synthesis and properties of cyclopropane derivatives of polybutadienes

Polymer products containing methoxycarbonyl-substituted cyclopropane groups in macromolecules with degrees of functionalization up to 40% have been obtained through the interaction of polybutadiene with methyl diazoacetate in an organic solvent in the presence of an organometallic catalyst. The comparative catalyst activity in the reaction of cyclopropanation of polybutadiene has been estimated. The incorporation of methoxycarbonyl-substituted cyclopropane groups into polydiene units results in substantial changes in the polymer properties: solution viscosity, melt flow, glass-transition temperature, and thermal stability.     

Preparation of Functional Poly(aroyltriazole)s by Metal-Free Click Polymerization

Functional poly(aroyltriazoles) (PATAs) were synthesized by heating mixtures of bis(aroylacetylene)s and diazides in polar solvents such as DMF/toluene at a moderate temperature of 100 °C with high molecular weights (M_w up to 17 200) and regioregularities (1,4-regioisomeric ratio up to ∼95%) in high yields (up to ∼95%). The obtained polymers are soluble in common organic solvents and are thermally stable. The PATAs containing triphenylamine units emit visible light and show unique solvatochromism, exhibiting large two-photon absorption cross sections due to the intramolecular charge transfer between their electron-donating triphenylamine and electron-accepting aroyltriazole units. The tetraphenylethene (TPE)-functionalized polymer shows intriguing aggregation-induced emission phenomenon, that is, the polymer is weakly emissive in its solution state but emit strongly in its aggregate/solid state with quantum yield of ∼7.1%.     

基于4,7-二噻吩苯并噻二唑和异靛单元的受体-受体共轭聚合物的合成与光伏性质

利用微波协助的Stille缩合聚合反应方法合成了基于双噻吩苯并噻二唑和异靛单元的受体-受体聚合物HFTBT-DA865,并对其热稳定性、光物理性能、电化学性质和本体异质结太阳能电池性能进行了研究.该聚合物易溶于邻二氯苯和邻二甲苯等溶剂,具有优异的溶液加工性能.5%热分解温度为389℃,玻璃化转变温度为168℃,说明其具有较好的热稳定性能.对旋涂速度和温度进行优化,所得太阳能电池器件的光电转换效率为2.28%,开路电压为0.83 V,短路电流为-5.70 mA/cm^2,填充因子为48.9%.电化学性能和密度泛函理论估算结果表明,聚合物与受体材料PC71BM相近的最低未占分子轨道(LUMO)值及其平面性可能是影响光伏性质的重要因素.通过调控共聚单体或优化受体材料,器件性能可进一步提高.对受体-受体(A-A)类聚合物材料太阳能电池性能的研究表明,此类材料是一类潜在的聚合物太阳能电池材料.