两性高分子与小分子及大分子的相互作用（上）

两性高分子是分子链上同时含有正负电荷基团的一类高聚物,具有独特的性质.本文就合成两性高分子与小分子物质(金属离子、表面活性剂、染料、有机探针等)及大分子化合物(聚电解质、蛋白质)的络合过程及影响络合的因素进行了综述.     

甲基丙烯酸3-磺酸丙酯钾盐苯乙烯共聚物负离子与N,N,N-三甲基十六烷基溴化铵相互作用研究

聚电解质与表面活性剂相互作用研究已有很多报道[1～4],由于在很多方面与生物膜中脂质体-蛋白质间相互作用相似,从而近年来备受关注[5～6].作为带电荷的水溶性高分子,聚电解质与带相反电荷的表面活性剂分子可以形成规整性非常好的聚电解质表面活性剂复合物.Ａｎｔｏｎｉｅｔｔｔｉ等报道聚丙烯酸与十六烷基三甲基溴化铵(ＣＴＡＢ)形成规整的介规相(Ｍｅｓｏｐｈａｓｅ)聚电解质表面活性剂复合物结构[7],漆宗能等在同一体系既观察到了热致液晶也观察到了溶致液晶[8].在研究甲基丙烯酸3磺酸丙酯钾盐(ＳＰＭＳ)的苯乙烯(Ｓｔ)共聚物(Ｐ(ＳＰＭ…     

酞菁铜衍生物与聚电解质的自组装

用原子力显微镜研究了阿利新蓝(Alcian Blue)和聚电解质自组装膜的表面形貌结构以探讨染料小分子的静电自组装途径。并通过将氯甲基酞菁小分子挂接在高分子链上，制备了一种高分子染料，然后和聚电解质组装成一种高分子复合物。     

水溶性高分子聚集行为荧光非辐射能量转移研究进展

评述了近几年荧光非辐射能量转移有疏水改性聚电解质的疏水聚集、高分子水溶液相变伴随的分子链塌陷、水溶性高分子与表面活性剂的相互作用等研究中的新进展,阐明了非辐射能量转移技术在水溶性高分子研究中的重要作用。     

重氮树脂型聚电解质复合物与SDS相互作用研究

由于聚电解质与表面活性剂的相互作用具有很多特别的性质而倍受关注［１～１０］,但具有感光性的重氮树脂作为正离子聚电解质与表面活性剂相互作用尚未见报道．本文研究了重氮树脂（ＤＲ）与聚苯乙烯磺酸钠（ＰＳＳ）形成的聚电解复合物（ＤＲ－ＰＳＳ）与十二烷基硫酸钠...     

高分子与表面活性剂在水相中的相互作用

按照组分荷电属性的不同,高分子/表面活性剂体系可大致划分为三种:中性高分子/离子表面活性剂体系、带电高分子/离子表面活性剂体系、高分子/非离子表面活性剂体系。本文对这三种体系在水相中的高分子/表面活性剂相互作用研究进行综述。在大多数情况下,水相中高分子与表面活性剂共存时都能发生相互作用并形成复合物,其驱动力主要包括疏水作用、静电作用和氢键作用。根据高分子与表面活性剂的荷电情况及结构性质(如疏水链长度)的不同,上述驱动力可以单独或组合作用。此外,温度、pH值、电解质等外界因素对复合物形成过程及结构也具有不同程度的影响。     

DNA与两性表面活性剂相互作用研究

本文综述了DNA与两性表面活性剂相互作用的研究进展，主要介绍了利用荧光显微镜、动静态光散射、相图及浊度等方法对DNA与两性表面活性剂相互作用的观察与形成复合物的表征。由于两性表面活性剂所具有的独特性质，可以实现在特定pH范围通过静电作用诱导DNA构象发生线圈状向小球状的不连续转变，并可通过调节溶液pH值、离子强度等实现对DNA-两性表面活性剂复合物的稳定性的调控。DNA与两性表面活性剂相互作用形成的复合物在非病毒基因载体研究方面具有潜在的应用价值。     

两性聚电解质PDMA_m-b-PAA_n与表面活性剂(12-6-12)的相互作用

采用Zeta电位、荧光探针、表面张力和黏度等方法研究了碱性条件下不同嵌段比的两性聚电解质聚(N,N-二甲胺基甲基丙烯酸乙酯-b-丙烯酸)(PDMAm-b-PAAn)与阳离子偶联表面活性剂(C12 H25(CH3)2N(CH2)6N(CH3)2C12H25·2Br-)(简称12-6-12)的相互作用.结果表明:由于静电相互作用,两嵌段聚电解质PDMAm-b-PAAn和12-6-12之间可形成类胶束或复合物,PDMA链段的弱亲水性对复合物起到稳定的作用.对同一类型的两嵌段聚电解质,改变两链段的相对长度之比,既不会使其在溶液中的构象发生改变,也不会使其与表面活性剂的相互作用模式发生改变.     

大离子诱导聚电解质/表面活性剂复合物的解离

采用分子动力学模拟方法研究了大离子与聚电解质/表面活性剂复合物的相互作用, 考察了大离子的电性、直径、表面电荷、浓度等对其与复合物相互作用的影响. 结果表明, 与聚电解质所带电性相同的大离子对复合物作用不明显, 只有当大离子所带电荷较多时, 才会引导少量表面活性剂从复合物中脱离. 当大离子所带电荷与聚电解质所带电荷电性相反时, 大离子的加入会诱导复合物的解离, 表面活性剂从复合物中释放出来, 甚至导致聚电解质/表面活性剂复合物的完全解离, 从而形成聚电解质/大离子复合物; 大离子所带电荷越多, 诱导作用越明显. 大离子的直径及浓度对其与复合物之间的作用也有很大的影响, 对于所带电荷数相同的大离子而言, 直径越小, 其与复合物的作用越显著, 越容易引导表面活性剂从复合物中解离, 若大离子的表面电荷密度相同, 大离子直径越小, 反而与复合物的作用越弱; 大离子浓度越高, 越易引起复合物的解离, 复合物中聚电解质链上结合的大离子数增多直至饱和, 相应的会出现电荷反转现象.     

正负离子表面活性剂与两性表面活性剂的相互作用

本文研究正负离子表面活性剂与两性表面活性剂混合水溶液的表面性质, 以及两性表面活性剂对正负离子裘面活性剂溶解度的影响。结果表明: (1) 两性表面活性剂的加溶作用,有助于正负离子表面活性剂的溶解; (2) 加入两性表面活性剂的量适当, 混合溶液基本保持原正负离子表面活性剂的表面活性; (3) 正负离子表面活性剂与两性表面活性剂在表面层和胶团中分子间的相互作用比正负离子表面活性剂与非离子表面活性剂分子间的相互作用稍强HC-FC正负; 离子表面活性剂与两性表面活性剂混合体系在表面层中有可能形成双分子或多分子层结构。     

Dichloropentafluoropropanes as solvents for size exclusion chromatography

We have found that HCFC225s (HCFC225ca: 3,3-dichloro-1,1,1,2,2-pentafluoropropane, HCFC225cb: 1,3-dichloro-1,1,2,2,3-pentafluoropropane) are superior mobile phases for size exclusion chromatography (SEC). As alternatives of CFC113, they have been shown to possess a number of excellent properties, such as low flammability, low viscosity, low cost, high purity, and environmental and operational friendliness. In addition, they have distinct advantages for the SEC measurement, because they solubilize some kinds of acrylate such as poly(methyl methacrylate) (PMMA) and commercial monodispersed PMMA can be used to prepare calibration curves necessary for the measurement of equivalent molecular weight of some polymers. Furthermore, we propose an HCFC225/1,1,1,3,3,3-hexafluoroisopropanol mixed solvent for use in the SEC of poly(ethylene terephthalate) (PET) and polyamides. Poly(2-(perfluorooctyl)ethyl acrylate), whose PMMA equivalent weight average molecular weight was 118,100 Da, was evaluated by a multi-angle laser light scattering (MALLS) detector to have an absolute molecular weight of 439,000 Da. The difference can be attributed to the molecular size of the polyfluorinated polymer compared to the non-fluorinated one. The possible application of this novel mobile phase system for molecular size and molecular weight characterization of perfluoropolyethers, PET, nylon 6 and nylon 6,6 are also discussed.     

Laser light scattering as GPC detector

The use of low angle laser light scattering (LALLS) as a detector in gel permeation chromatography (GPC) is discussed. The advantage of this technique is primarily based on the ability of LALLS to continously measure the absolute molecular weight and also to detect minute concentrations of high molecular weight species such as microgel. The weakness of the system is in the low sensitivity for low molecular weight material. In this paper, our experience of the KMX-6 from Chromatix illustrates the possibilities for the characterization of polymers by the combination of LALLS and GPC. The applications discussed are mainly from our work with polyethylene and poly(vinyl chloride). Special emphasis is given to the determination of long chain branching and microgel.     

Titanium alkoxides as initiators for the controlled polymerization of lactide

Fourteen titanium alkoxides were synthesized for comparison of their catalytic properties in the bulk and solution polymerization of lactide (LA). In bulk polymerizations, they are effective catalysts in terms of polymer yield and molecular weight. Titanatranes gave polylactides with significantly increased molecular weight over more extended polymerization times, and those with five-membered rings afforded polymers in higher yields and with larger molecular weights than their six-membered ring counterparts. Steric hindrance of the rings was found to significantly affect polymer yields. Increased heterotactic-biased poly(rac-LA) was formed as the number of chlorine atoms increased in TiCl(x)(O-i-Pr)(4)(-)(x). In solution polymerizations, titanium alkoxides catalyzed controlled polymerizations of LA, and end group analysis demonstrated that an alkoxide substituent on the titanium atom acted as the initiator. That polymerization is controlled under our conditions was shown by the linearity of molecular weight versus conversion. A tendency toward formation of heterotactic-biased poly(rac-LA) was observed in the solution polymerizations. The rate of ring-opening polymerization (ROP) and the molecular weight of the polymers are greatly influenced by the substituents on the catalyst, as well as by factors such as the polymerization temperature, polymerization time, and concentration of monomer and catalyst.     

Uniform oligomers as reference materials for molecular weight determination of polymers

 Uniform oligomers are special oligomers having no molecular weight distribution. They have been used as reference materials for polymer characterization, especially for accurate molecular weight determination in lower molecular weight ranges. These oligomers are used for different purposes. First, they are used in the calibration for chromatographic or spectroscopic data. Second, they are applied to identifying peaks appearing in chromatographies such as supercritical fluid chromatography (SFC) of oligomeric mixtures. Finally, they could give accurate instrumental or physicochemical constants used in polymer characterizations. The uniform oligomers have been prepared by using preparative chromatographies as separation methods. In some cases, step-wise syntheses have been applied together with the chromatographic methods. Recently, we prepared uniform oligostyrenes and oligo(oxyethylene)s whose molecular weights are greater than 1000 by using preparative size exclusion chromatography. More recently, using preparative SFC, some Japanese researchers have prepared high molecular weight and uniform oligomers such as oligo(methylmethacrylate)s. In this article, we briefly review recent progress mainly made by Japanese researchers in the field of preparation, analysis and applications of these pure oligomers. Received: 20 September 1996 Accepted: 3 December 1996     

Photo-living radical polymerization of methyl methacrylate using alkoxyamine as an initiator

The photoradical polymerization of vinyl acetate was performed using 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl (MTEMPO) as the mediator in the presence of bis(alkylphenyl)iodonium hexafluorophosphate (BAI). The MTEMPO/BAI system using 2,2’-azobis(isobutyronitrile) or 2,2’-azobis(4-methoxy-2,4-dimethylvaleronitrile) as the initiator did not succeed in controlling the molecular weight and produced polymers that showed a bimodal gel permeation chromatography with the broad molecular weight distribution. On the other hand, the polymerization using 1-(cyano-1-methylethoxy)-4-methoxy-2,2,6,6-tetramethylpiperidine and BAI proceeded by the living mechanism based on linear increases in the first order time–conversion and conversion–molecular weight plots. The molecular weight distribution also increased with the increasing conversion due to cloudiness of the solution as the polymerization proceeded. It was found that the polymerization had a photolatency because the propagation stopped by interruption of the irradiation and was restarted by further irradiation.     

Photoinduced ATRP of acrylonitrile with aniline as photoinitiator

Photo-mediated atom transfer radical polymerization (ATRP) of acrylonitrile (AN) was carried out at 25°C in N,N-dimethyl formamide (DMF) with aniline as photoinitiator. Polyacrylonitrile (PAN) with predictable average molecular weight and narrow molecular weight distribution was synthesized with 2-Bromopropionitrile (BPN) as ATRP initiator and FeCl₃·6H₂O/Triphenylphosphine (PPh₃) as the catalyst. The obtained kinetics showed that the photoinduced Fe-mediated ATRP of AN provided a route to synthesize well defined PAN with narrow molecular weight distribution (M_w/M_n). The living character of photoinduced Fe-mediated ATRP of AN was verified by the linear increase of molecular weights with monomer conversion and the molecular weights are in good agreement with the theoretic values. In addition, the chain extension experiments were successfully conducted under the same conditions. The periodic light on-off process was investigated for the photoinduced Fe-mediated ATRP of AN. The obtained PAN was characterized by ¹H nuclear magnetic resonance and gel permeation chromatography. The brominated PAN was used to perform chain-extension with AN as macroinitiator in order to verify the living nature of photoinduced ATRP of AN-Br.     

Effects of Hofmeister Anions on the LCST of PNIPAM as a Function of Molecular Weight

The effect of a series of sodium salts on the lower critical solution temperature (LCST) of poly(N-isopropylacrylamide), PNIPAM, was investigated as a function of molecular weight and polymer concentration with a temperature gradient microfluidic device under a dark-field microscope. In solutions containing sufficient concentrations of kosmotropic anions, the phase transition of PNIPAM was resolved into two separate steps for higher molecular weight samples. The first step of this two step transition was found to be sensitive to the polymer's molecular weight and solution concentration, while the second step was not. Moreover, the binding of chaotropic anions to the polymer was also influenced by molecular weight. Both sets of results could be explained by the formation of intramolecular and intermolecular hydrogen-bonding between polymer chains. By contrast, the hydrophobic hydration of the isopropyl moieties and polymer backbone was found to be unaffected by either the polymer's molecular weight or solution concentration.     

Low-density polyethylene: Variation of branching frequency with molecular weight and its influence on molecular weight as determined by gel-permeation chromatography

A method for determining long-chain branching frequency and molecular weight averages for unfractionated low-density polyethylene (LDPE) by the combined use of gel-permeation chromatography (GPC) and intrinsic viscosity data has been reported (GPC–IV method). The method assumes that the number of long branches λ per unit molecular weight is a constant independent of molecular weight. Recent data reported on λ as a function of molecular weight M in commercial LDPE indicate that this assumption is not generally valid, and concern has been expressed as to the size of the errors in molecular weights calculated using this assumption. The errors associated with assuming that λ is constant were evaluated in this study by first determining the way in which λ varies with M for two typical commerical LDPE resins by fractionation and application of the GPC–IV method to representative fractions. The experimentally determined relations between λ and M were then employed in the calculation of molecular weight and molecular size averages from GPC–IV data on the original unfractonated samples. Although it was found that λ increases with molecular weight for both samples, the results indicate that the error involved in assuming that λ is a constant is no greater than the precision with which molecular weight averages can be evaluated by GPC.     

Interaction between poly(ethylene glycol) and water as studied by differential scanning calorimetry

The interaction between poly(ethylene glycol) (PEG) and water was studied by differential scanning calorimetry (DSC). The DSC curves of PEG–water systems were classified into three groups according to the difference in molecular weight. The melting peaks of eutectic mixture appeared for PEG with molecular weight higher than 1000. The eutectic point temperature shifted to higher temperatures and the eutectic point composition shifted to lower concentrations of PEG with increasing molecular weight. The maximum hydration number per ethylene glycol (EG) unit was estimated as 1.6, 2.4, and 3.3 for samples with molecular weights 400, 1540, and 70,000, respectively. No thermal change was found in PEG1540‐water system for a narrow weight fraction range of 0.585–0.605 for overall measuring temperatures due to perfect supercooling. The glass transition temperature shifted to higher temperatures with increasing molecular weight of PEG. A modified Flory–Huggins equation was used to fit curves for experimental liquidus data in phase diagrams. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 496–506, 2001     

Photo-controlled/living radical polymerization of 2-(dimethylamino)ethyl methacrylate using 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl as a mediator

The photo-controlled/living radical polymerization of 2-(dimethylamino)ethyl methacrylate (DMAEMA) was attained using 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl as the mediator and (2RS,2′RS)-azobis(4-methoxy-2,4-dimethylvaleronitrile) (r-AMDV) as the initiator. The bulk polymerization of DMAEMA produced a polymer with a comparatively narrow molecular weight distribution below 1.6. The first-order time conversion plots showed a linear increase. The molecular weight of the resulting polymer also increased with an increase in the monomer conversion. The molecular weights of the resulting polymers were in good agreement with the theoretical molecular weights. A linear correlation was also obtained for the plots of the molecular weight vs. the reciprocal of the initial concentration of r-AMDV. The GPC analysis demonstrated the living nature of the polymerization based on the fact that the curves were shifted to the higher molecular weight side without deactivation as the conversion increased.