Study of copolymer–copolymer interactions and formation of intermacromolecular complexes

Interpolymer complex formation has been studied between methacrylic acid-methacrylamide copolymer and acrylic acid–acrylamide copolymer. The respective co-monomer units of the two copolymers enter into complex formation through H-bonding and ion dipole interactions. The unreacted units in the copolymer complex also interact with homopolymers such as PEO and PVP to form ternary complex. Formation of complexes and replacement reactions could be shown through several experimental techniques, e.g., viscometry, conductometry, and potentiometry.     

Photooxidative and pyrolytic degradation of methyl methacrylate-alkyl acrylate copolymers

Different compositions of poly(methyl methacrylate-co-methyl acrylate) (PMMAMA), poly(methyl methacrylate-co-ethyl acrylate) (PMMAEA) and poly(methyl methacrylate-co-butyl acrylate) (PMMABA) copolymers were synthesized and characterized. The photocatalytic oxidative degradation of all these copolymers were studied in presence of two different catalysts namely Degussa P-25 and combustion synthesized titania using azobis-iso-butyronitrile and benzoyl peroxide as oxidizers. Gel permeation chromatography (GPC) was used to determine the molecular weight distribution of the samples as a function of time. The GPC chromatogram indicated that the photocatalytic oxidative degradation of all these copolymers proceeds by both random and chain end scission. Continuous distribution kinetics was used to develop a model for photocatalytic oxidative degradation considering both random and specific end scission. The degradation rate coefficients were determined by fitting the experimental data with the model. The degradation rate coefficients of the copolymers decreased with increase in the percentage of alkyl acrylate in the copolymer. This indicates that the photocatalytic oxidative stability of the copolymers increased with increasing percentage of alkyl acrylate. From the degradation rate coefficients, it was observed that the photocatalytic oxidative stability follows the order PMMABA > PMMAEA > PMMAMA. The thermal degradation of the copolymers was studied by using thermogravimetric analysis (TGA). The normalized weight loss and differential fractional weight loss profiles indicated that the thermal stability of the copolymer increases with an increase in the percentage of alkyl acrylate and the thermal stability of poly(methyl methacrylate-co-alkyl acrylate)s follows the order PMMAMA > PMMAEA > PMMABA. The observed contrast in the order of photostability and thermal stability of the copolymers was attributed to different mechanisms involved for the scission of polymer chain and formation of different products in both the processes.     

Formation of polymer–colloid complexes of aluminoxane particles with poly(acrylic acid) and its copolymers with acrylamide

Formation of polymer–colloid complexes formed by positively charged aluminoxane particles with a size of ~4.6 nm, which constitute the main part of the dispersed phase in aluminum polyhydroxychloride sols with poly(acrylic acid) and acrylic acid copolymers with acrylamide, is studied. Conditions of preparing water-soluble polymer–colloid complexes are determined. It is shown that water-soluble polycomplexes are obtained through the interaction of aluminoxane particles with acrylic acid–acrylamide copolymers containing no more than 0.8 mol% acrylic acid units. In the polymer–colloid complex, aluminoxane particles are uniformly distributed over polyelectrolyte macromolecules and the optimum composition is attained at the molar ratio of components Z equal to 1:1. In semidilute solutions, the addition of aluminoxane particles to the copolymer brings about formation of the gel featuring viscoelastic properties. For all copolymers, the maximally elastic properties of the gels are attained at Z ≈ 1.     

部分水解聚丙烯酰胺-羟乙基纤维素的水相pH响应性自组装

为考察无规共聚物在全水相环境中的自组装行为, 合成了结构类似于无规共聚物的低相对分子质量的部分水解聚丙烯酰胺(HPAM). 尝试改变水溶液pH值来诱导HPAM与羟乙基纤维素(HEC)发生自组装, 采用透射电子显微镜(TEM)观察到不同pH值时分别获得了100 nm的似正方体胶束, 200 nm×100 nm的类椭球胶束, 100 nm的串珠状胶束以及500 nm×300 nm×50 nm的半月形胶束等pH响应性核壳型聚合物胶束. 建立了金在胶束表面原位还原耦合TEM表征方法, 用于检测低衬度聚合物胶束的纳米细节; 配合电子探针X射线微区分析(EPMA)和扫描电子显微镜(SEM), 证实了半月形聚合物胶束的精致分级构造为亲水性内囊@疏水性连续囊壁@亲水性外壳的多泡囊泡, 并证实pH=0.9时多泡囊泡崩解为疏水性内核@亲水性外壳的10 nm类球体小胶束. 通过分析链节质子化状态的pH响应性, 结合zeta电位和吸光度测定结果, 阐释了不同pH值时组成聚合物胶束的核和壳的链段归属, 获得了全水相中HPAM自组装驱动力和形貌方面的全新知识.     

Conformational and hydrodynamic properties of the homopolymer of 2-deoxy-2-methacrylamido-D-glucose and its copolymers with acrylic acid and methacrylic acid

Hydrodynamic properties of the homologous series of the homopolymer 2-deoxy-2-methacryla-mido-D-glucose and the copolymers of 2-deoxy-2-methacrylamido-D-glucose with unsaturated acids in 0.2 M NaCl are studied via static and dynamic light scattering, viscometry, refractometry, and translational diffusion. The copolymers synthesized via the free-radical copolymerization of 2-deoxy-2-methacrylamido-D-glucose with acrylic acid or methacrylic acid contain ～20 mol % acid units. At this amount of acid units, the equilibrium rigidity of copolymer chains corresponds to that of homopolymer chains. The copolymers are distinguished by the hydrodynamic characteristics of molecules. The copolymer with methacrylic acid is similar to the homopolymer, whereas the copolymer with acrylic acid features substantially different parameters of relationships relating the hydrodynamic characteristics of homologs to their molecular masses.     

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…     

模板聚合法合成P(AM/AA)多嵌段共聚物的溶液性质和自缔合作用

研究了模板法合成多嵌段状丙烯酰胺(AM)和丙烯酸(AA)共聚物(简称模板共聚物TP)在水溶液中的溶液性质和缔合作用.结果表明,模板共聚物具有明显的结构效应.不同于无模板参与聚合的无规共聚物(CP),模板共聚物随着溶液pH的降低或加入多价金属离子容易发生相分离.透射电子显微镜(TEM)表明,加入Ca2+离子后,聚合物形成了大的分子间交联体,且随着Ca2+离子浓度的增加,交联程度增加,致使溶液产生相分离.随着溶液pH的升高,模板共聚物溶液粘度变化与丙烯酸均聚物具有相同的规律,都是先增大后减小,粘度有一个最大值,但模板共聚物溶液粘度升高幅度更大.TEM表明在粘度最大处形成了带状分子间缔合体.     

Grafting on Some Phenolic Copolymer Chains

A phenolic copolymer has been prepared by copolymerization of p-chlorophenol, p-cresol, and formaldehyde in the presence of acid catalyst. The copolymer was partially and completely dehalogenated by a standard method. The dehalogenated copolymer chain had a random distribution of reactive positions which were originally occupied by Cl atoms. Some substituted monomers, oligomers of known structure and molecular weight, and basic polymer chains have been grafted at these reactive positions. The halogen percentage of the grafted copolymers could be calculated on the assumption that all the available reactive positions are attached to the respective units. Reasonably good agreement has been found between the calculated and observed amount of halogen percentage in the grafted copolymers.     

腐植酸接枝共聚物对赤红壤K~+吸附与解吸的影响

本文研究了经施用硝基腐植酸与丙烯酸、丙烯酰胺三元接枝共聚物的赤红壤中钾离子的吸附和解吸的影响。实验结果表明,施用共聚物的土壤可减少土壤对中钾离子的吸附,增加土壤对钾离子的解吸,提高钾离子的抗淋溶。改良后的土壤可减少土壤钾的损失,提高钾肥的利用率。     

Structural Effect and Composition of Anionic Copolymer on Protein Flocculation

Flocculation of lysozyme with anionic copolymers of acrylamide, acrylic acid, and sodium styrene sulfonate used as flocculants was performed in pursuit of high flocculation efficiency. Two major factors, pH and ionic strength, are used to investigate the relationship of the flocculation behavior of protein by copolymers and the functional group (–COOH, –NH₂, –SO₃H) compositions of these copolymers. The protein flocculation can be controlled by adjusting pH. In addition, the various copolymers exhibit differing effects on ionic strength induced protein flocculation. FT-Raman spectroscopy was applied to investigate the mechanism of interaction between protein and copolymer. An attempt was made to understand how the pH and ionic strength change the surface chemical characteristics of protein and copolymers, as well as the relationship between the structure of copolymer and the protein flocculation process.     

Effect of introducing acrylic and methacrylic acid groups on molecular relaxation of poly(ethyl methacrylate)

Dielectric and infrared data have been obtained over a wide temperature range on copolymers of ethyl methacrylate with methacrylic and acrylic acid synthesized by radical copolymerization. The dissociation energy ΔH⁰ for the acid dimer in the copolymer is estimated from the temperature dependence of the relaxation strength Δε_α of the α relaxation, which is associated with the glass transition. The value of δH⁰ obtained by this method is in fair agreement with that determined by infrared (IR) spectroscopy. The strength of the α relaxation and its activation energy are both increased by the incorporation of methacrylic acid units but are decreased by acrylic acid units. This behavior is attributed to the restriction of main-chain motions by hydrogen-bonded acid dimers in the copolymers with methacrylic acid and to the incorporation of more flexible links in the copolymers with acrylic acid. The β relaxation observed below the glass transition temperatures is almost unaffected by the incorporation of methacrylic acid.     

Water-Soluble imide-amide copolymers. II. Preparation and characterization of poly (acrylamide-co-p-maleimidobenzoic acid)

The comonomer required, p-maleimidobenzoic acid (MBA) was first prepared in good yield by refinements of published methods. p-Carboxysuccinanilic acid (CSA), and p-succinimidobenzoic acid (SBA), were also prepared to provide models useful for IR and NMR for spectroscopic assignments of the new copolymers. Polymerization of MBA with acrylamide in glacial acetic acid at 60°C gave copolymers with estimated viscosity average molecular weights of 60,000 to 90,000. Yields and viscosity average molecular weights decreased as the MBA to acrylamide monomer feed ratio was increased. The rate of incorporation of MBA into the copolymer rose from 7 to 23% when the mole ratio in the feed was raised from 5 to 20%. Decreasing the initiator concentration increased molecular weights by less than predicted and reduced the yield of copolymer for any given feed ratio of MBA to acrylamide. In all cases about 30–40% of the MBA units in the purified copolymers were hydrolyzed. A change to dimethyl sulfoxide solvent gave good, and poor yields of copolymer at 5 and 10 mol % MBA, respectively, and no copolymer at 20 mol % MBA. Viscosity average molecular weights of the copolymer products prepared in DMSO were somewhat lower than obtained for the copolymers prepared in acetic acid. Polymerization in a DMSO-water mixture gave a negligible yield of polymeric product. Instead, only hydrolysates of MBA precipitated when the coloured polymerization solutions were added to methanol.     

INTERPOLYMER ASSOCIATION OF ACRYLAMIDE COPOLYMERS WITH POLY(ETHYLENEIMINE): STABILITY,THERMODYNAMIC PARAMETERS,AND THEIR CORRELATION WITH THE COPOLYMER MICROSTRUCTURE

Acrylamide/vinyl acetate and acrylamide/vinyl propionate copolymers were prepared by solution polymerization using benzoyl peroxide as the initiator. The copolymer composition was determined from the percent nitrogen in the copolymers.

The stability constants and related thermodynamic parameters (e.g., ΔG°, ΔH°, and ΔS°,) of the interpolymer complexes with Poly(ethyleneimine) were determined by using Osada's method. These parameters have been correlated with the sequence distribution of monomer units in the copolymer chains which were obtained from ¹³C{¹H} NMR spectroscopy. The sequence distribution of the comonomer units in the copolymer chains influence the association between the copolymers and the polyelectrolyte which is reflected on the stability of the interpolymer complexes.     

Direct Synthesis of Double Hydrophilic Statistical Di‐ and Triblock Copolymers Comprised of Acrylamide and Acrylic Acid Units via the MADIX Process

Double hydrophilic statistical, diblock and triblock copolymers comprised of acrylamide and acrylic acid units have been synthesized in aqueous medium using the MADIX process. Starting from an either monofunctional or difunctional xanthate, the resulting AB and ABA‐type double hydrophilic block copolymers (DHBC) exhibited molar masses predetermined by the initial monomer/xanthate precursor molar ratio and polydispersity indices in the range 1.2–1.5. Batch copolymerizations yielded well‐defined statistical copolymers that were chain‐extended for the synthesis of novel poly‐ (acrylic acid‐stat‐acrylamide)‐block‐polyacrylamide DHBC.     

Water soluble polymeric nanogels by xanthate-mediated radical crosslinking copolymerisation

Branched water-soluble copolymers were obtained by direct radical crosslinking copolymerisation of acrylic acid or acrylamide and N,N'-methylenebisacrylamide at high solid content in the presence of an O-ethylxanthate as a reversible chain transfer agent.     

Effect of copolymer architecture on the response of pH sensitive fibers based on acrylonitrile and acrylic acid

Copolymers of acrylonitrile and acrylic acid with high acrylic acid feed ratio of 43 mol% were synthesized using free radical polymerization. The architecture of copolymers was modified by regulating the dosing of more reactive comonomer-acrylic acid. ¹³C NMR analysis confirmed that two copolymers - one (A) containing enriched blocks of individual monomer-residues (architecture close to a block copolymer) and the second (B) having nearly random distribution of the comonomers, could be successfully synthesized. The resultant acrylic acid content was determined to be nearly 50 mol% for both the copolymers. These copolymers were converted to fine fibers by solution spinning in DMF-water system, drawn in coagulation bath, and annealed at 120 °C for 2 h. The fibers were evaluated for pH response behavior, mechanical stability, and retracting stresses. The fiber A was found to have significantly higher swelling percentage (3300-3700%), faster response, and higher stability to repeated cycling compared to fiber B. Also, Fiber A showed lower thermal shrinkage, better mechanical properties during swelling and higher retracting forces during deswelling. These results indicate that the copolymer with enriched block architecture could possibly form segregated domain structure with acrylic acid domains facilitating enhanced pH response while acrylonitrile domains providing physical crosslinks for stronger mechanical strength. The study suggests that above approach may be more useful than chemically cross-linked gel rods in producing artificial muscles with faster response and good mechanical properties.     

部分水解法制备高分子量水溶性(丙烯酰胺/丙烯酸/2-丙烯酰胺-2-甲基丙磺酸)三元共聚物

系列的高分子量水溶性丙烯酰胺 /丙烯酸 /2 丙烯酰胺 2 甲基丙磺酸 (AM/AA/AMPS)三元共聚物(P3A)由相应的 (AM/AMPS)二元共聚物通过部分水解方法制得 .聚合物的结构和组成使用电位滴定和13 C NMR谱测定 ,得到的结果指出 ,在设定的试验条件下 ,水解过程中 ,高分子链上AMPS单元具有充分的稳定性 ,而丙烯酰胺基平稳地转变为丙烯酸 .在所有不同聚合物 (P2A)情况下 ,由于阴离子基团和OH-离子的静电相斥作用 ,酰胺基的水解反应均遵循自动减缓动力学的模式 ,同时 ,最后反应转化率趋向极限 ,AM剩余值位于 3 0mol%左右 ,另外对各种三元共聚物 (P3A)的溶液特性粘数和组成的关系亦作了详细的研究 .     

AA-AM-AN三元共聚物的合成及其溶液性能的研究

采用自由基水溶液共聚法制备了水溶性丙烯酸－丙烯酰胺－丙烯腈共聚物。对聚合反应温度、引发剂用量、尿素用量、聚合物浓度、电解质浓度、剪切速率、温度等因素对聚合物溶液性能的影响进行了研究。结果表明,合成的水溶性聚合物具有良好的增稠作用及耐温抗盐抗剪切等性能。     

Effect of pH on the reactivity ratios in the copolymerization of acrylic acid and acrylamide

The content of acrylic acid and acrylamide in their copolymers can be controlled by changing pH. The reactivity ratio of acrylic acid decreases with increasing pH, while the reactivity ratio of acrylamide increases with increasing pH. At low pH values, acrylamide is present in its protonated form which causes its reactivity to be low whereas at high pH values the reactivity of acrylic acid is decreased owing to its dissociation. When the monomer and radical approach each other, the acrylate anion becomes the least reactive species because of its symmetrical charge distribution, like charge repulsion and barium ion screening effect. HMO calculations were performed for models of all monomers and polymer radicals involved in copolymerizations. The experimental results concerning the reactivity of acrylic acid and acrylamide in copolymerization and the observed reactivity ratios were discussed on the basis of HMO calculations and resonance and Coulomb electrostatic effects. The observed reactivity ratios were correlated with the calculated differences in resonance energies computed for the models of transition states involved in copolymerizations.     

The adsorption of cationic and amphoteric copolymers on glass surfaces: zeta potential measurements,adsorption isotherm determination,and FT Raman characterization

The adsorption of cationic and amphoteric copolymers onto controlled pore glass (CPG) powders has been studied by measurement of the powder particle zeta (zeta) potential, by determination of the adsorption isotherm, and by FT Raman measurements of the polymer-coated powder. The cationic polymers consisted chiefly of homopolymers of dimethyldiallylammonium chloride (DMDAAC) or copolymers of DMDAAC and acrylamide. The amphoteric polymers studied included copolymers of DMDAAC and acrylic acid. The comonomer ratio was varied to explore the dependence of cationic charge density on the extent and effect of adsorption. Both types of polymers adsorb onto the anionic glass surface via an ion-exchange mechanism. Consequently, a correspondingly higher mass of a low-charge-density copolymer adsorbs than of a cationic homopolymer. The presence of the anionic portion in the amphoteric polymers does not significantly alter this picture. The zeta potential, however, reflects the overall nature of the polymer. Cationic polymers effectively neutralize the glass surface, while amphoteric polymers leave the zeta potential net negative. Adsorption isotherms, determined via the depletion technique using colloidal titration, were used to "calibrate" a FT Raman method. The latter was used to determined the amount of adsorbed polymer under solution conditions in which colloidal titration could not be performed.