聚丙烯酸/聚丙烯酰胺水溶液复合特性的研究

通过酸度、电导率、粘度、接触角的测定,研究了聚丙烯酸 (PAA) /聚丙烯酰胺 (PAM) 水溶液复合物及复合物膜的结构和性能。结果表明,酸度、温度、浓度和复合比影响PAA/PAM的复合水溶液中大分子链的构象和流体力学体积,适度的氢键作用可以形成均相的复合溶液。经过热处理和未经热处理的聚合物膜表现出了不同的亲水性能。     

聚丙烯酸环境响应行为的研究

采用介观动力学分子模拟(Mesodyn)和耗散颗粒动力学(DPD)分子模拟与流变等实验技术相结合的方法, 研究了pH/无机盐敏感聚合物聚丙烯酸PAA在水溶液中的环境响应行为, 考察了聚合物浓度、溶液离子强度、聚合物表面电荷对PAA相行为的影响. 实验结论与模拟结果符合得很好, 对照分析给出了聚丙烯酸的环境响应机制, 为设计和应用环境敏感的智能体系提供指导和理论依据.     

Sorption of Water Vapor by Keratin

The word “keratin” is usually applied to that group of fibrous proteins characterized by the presence of the amino acid cystine which enables the formation of disulfide bridges between neighboring polypeptide chains. In nature, the hardened form of keratin plays a protective role and appears in many forms of animal outer covering, such as wool, hair, nails, horn, feather, and quill, where a high degree of physical strength and chemical resistance are desirable. This variety provides a wide selection of geometrical forms and subtle differences in composition between keratins, which can be employed in the study of sorption mechanisms for this material. All forms of keratin contain hydrophilic amino acid residues and peptide groups which ensure significant adsorption of water vapor. Keratin differs from the soluble proteins because the presence of cross-links renders it insoluble in water; it is only soluble in reagents capable of rupturing the disulfide bridges. However, in common with other biopolymers and synthetic polymers having an affinity for water, keratin swells on adsorption over the entire humidity range.     

Thermodynamics of Swelling of Poly(N-vinylpyrrolidone)-Poly(ethylene glycol) Complex Due to Water Sorption

The deformation of sorbent caused by the sorption is new method of quantitative investigation “in situ” of interaction in system host-quest. The deformation of PVP-PEG complex, ϕ_PEG=0.36 and ϕ_PEG=0.20 due to water sorption has been studied by the measuring of the relative elongation of the polymer samples and the isotherms of water sorption simultaneously. The investigation of the sorption deformation gives the possibility of direct estimation of polymer sample free volume and it's variation during sorption, also the variation of Gibbs energy of system due to sorption according to the vacancy solution theory. The glassy-plastic state transition of polymer during water sorption has been observed.     

Catalytic Hydrogenation over Palladium Complex of Molecular Complex of Poly(4-vinylpyridine) with Acetic Acid

The palladium complex of the molecular complex of poly(4-vinylpyridine)with acetic acid (PVP/HAc-Pd) was prepared.Its catalytic activity for the hydrogenation of nitrobenzene was found much higher than that of the corresponding palladium complex of poly(4-vinylpyridine).In the presence of a strong inorganic alkali.especially potassium hydroxide.the catalytic activity is greatly improved.The suitable hydrogenation condition for PVP/HAc-Pd is to use 0.1mol/L ethanol solution of potassium hydroxide as the hydrogenation medium and the hydrogenation is carried out at 45 ℃。     

Supramolecular Complex of Poly(styrene)-b-Poly(4-vinylpyridine) and 1-Pyrenebutyric Acid in Thin Film

Summary: Here, we have described a novel supramolecular complex (SMC) between poly(styrene)-b-poly(4-vinylpyridine) (PS-b-P4VP) and 1-pyrenebutyric acid (PBA) and studied of its self assembly in thin film. PBA will make supramolecular complex with the P4VP block due to strong hydrogen bonding between the carboxylic group of 1-pyrenebutyric acid and pyridine ring of P4VP. The formation of supramolecular complex between PS-P4VP and PBA through hydrogen bonding is investigated through FTIR study. The supramolecular complex of PS-b-P4VP and 1-pyrenebutyric acid changed the block copolymer morphology from cylindrical to lamella in thin film due to the increase of the volume fraction of P4VP (PBA). In both cases (parent block copolymer and SMC), the microdomains are oriented normal to the substrate after annealing in a selective solvent. Pure block copolymer shows cylindrical morphology with a periodicity of ∼26 nm, whereas the SMC shows lamellar morphology with a periodicity of ∼ 29 nm. After fabricating the thin film from SMC, 1-pyrenebutyric acid can be easily removed by dissolving the thin film in ethanol to transform the block copolymer thin film into nanotemplate or membrane.     

壳聚糖／聚丙烯酸聚电解质复合物膜对水／有机液体系的渗透汽化性能

以壳聚糖和聚丙烯酸为原料制备了聚电解质复合物膜，并对其分离水／乙醇体系的渗透汽化特性和浓度，温度，化学组成等因素的影响进行了研究，发现后处理方法对复合物膜的分离性能影响很大。同时对其它水／有机液体系，该膜也具备优异的分离性能。     

非离子聚(N-乙烯基-2-吡咯烷酮)凝胶在线型聚(丙烯酸)溶液中的溶胀特性

研究了在线型聚 (丙烯酸 ) (PAA)溶液中链长、pH、离子强度和水 /二甲亚砜混合溶剂组成对非离子聚 (N-乙烯基 - 2 -吡咯烷酮 ) (PVP)水凝胶溶胀特性的影响 .发现聚酸浓度的变化引起凝胶显著的体积相变 ,这是因为凝胶和聚合物通过氢键形成了大分子间凝胶 -聚合物复合物 .凝胶的溶胀特性取决于聚酸的链长而不是离子强度 .随着pH值和水 /二甲亚砜混合溶剂组成的变化 ,凝胶的溶胀率 (SR)发生变化     

A Safety Strategy for Producing Poly(Acrylic Acid) of Low Molar Mass

The synthesis of poly(acrylic acid) (PAA) of low molar mass under safe conditions is difficult due to the high polymerization rate of acrylic acid (AA) and the fast heat generation. The aqueous‐solution “semibatch” polymerization of non‐ionized AA in almost starved conditions involves high initiator loads when low molar masses are required. This article proposes the simultaneous feeding of AA and nonconventional chain transfer agents (CTA) as a strategy aimed at controlling both the molar masses and the generated heat rate. Three CTAs are investigated: 2‐mercaptoethanol, thioglycolic acid, and isopropyl alcohol. Even when PAA of relatively low molar mass can be produced by adequately selecting the flow rates and concentrations of both AA and CTA, it is found that the nature of CTA can have a significant effect on the polymerizations kinetics. The mechanisms responsible for these effects are discussed with the help of a representative mathematical model.

     

Modification of Poly(Ethylene Terephthalate) Track Membranes by Sorption of Poly(Ethylene Glycol)

Sorption of poly(ethylene glycol) on poly(ethylene terephthalate) track membranes was studied at different pH. The hydrophilic-hydrophobic properties of the intact membranes and those modified with poly(ethylene glycol) are compared. The membrane-aqueous human serum albumin and membrane-aqueous insulin adhesive tensions were determined for modified membranes. The competitive sorption of human serum albumin and poly(ethylene glycol) from aqueous solution on the track membranes is analyzed.     

Scale Inhibitor and Dispersant Based on Poly(Acrylic Acid) Obtained by Redox‐Initiated Polymerization

Low molar mass poly(acrylic acid) (PAA) is generally obtained by free radical polymerization of acrylic acid (AA) in aqueous solution, using thermal initiators and some chain transfer agent. However, under such conditions it is rather difficult to efficiently produce molar masses as low as those required for obtaining an effective dispersant. In this work, the semibatch polymerization of AA at 45 °C is considered, using potassium persulfate (KPS) and sodium metabisulfite (KPS/NaMBS), or alternatively KPS and sodium hypophosphite (KPS/NaHP) as redox initiators to produce PAA of controlled low molar masses. These initiation systems allow the production of PAA with M_n as low as 2.0 kDa, relatively narrow molar mass distribution (1.5 < M_w/M_n < 3.0), and low branching degree. Most of the investigated polymerizations reach almost complete conversions (>95%); and it is verified that both reductants, NaMBS and NaHP, also behave as chain transfer agents. Finally, the investigated process with redox couples allowed the production of PAA with acceptable dispersant and antiscaling properties.     

Functionalization of Poly[Ethylene Terephthalate) by Means of Glow-Discharge-Initiated Polymerization of Acrylic Acid

Glow-discharge-initiated polymerization of acrylic acid incorporated in poly(ethylene terephthalate) (PET) films was investigated. An increase in polymerization yield with plasma treatment duration and power was found. Polymerization was not confined to the film surface. At high power and long treatment time, polymerization in the bulk of the PET also took place. Water regain and contact angle of the PET-treated films were affected by the presence of poly(acrylic acid) (PAA). The carboxyl groups of the PAA chains incorporated in the PET matrix were utilized for further chemical modification of the PET film. Poly(ethylene glycol) (PEG) was grafted onto PAA by esterification. DSC studies showed the presence of both PAA and PEG in the PET matrix and shed light on the morphology of the multicomponent polymeric system. Free isocyanate groups were introduced into the PET matrix by reacting PAA carboxyl groups with hexamethylene diisocyanate.     

Interaction of Nonionic Block Copolymeric (Poloxamer) Surfactants with Poly (Acrylic Acid), Studied by Photon Correlation Spectroscopy

The interaction between certain hydrophilic pluronic (poloxamer) surfactants and a poly (acrylic acid) has been investigated. Both the PPO and the PEO groups of the surfactants, and the -COOH groups and aliphatic side chains of the PAA molecule, were found to be crucial in this interaction to form complexes. At pH 2 and with a low poloxamer:PAA molar ratio, maximum interaction was observed, giving rise to large-sized complexes that were unstable but possessing bioadhesive properties. At the same pH but with higher poloxamer:PAA molar ratio, the complexes became smaller in size and more stable and were used to prepare stable w/o/w emulsions. A further increase in the poloxamer:PAA molar ratio or increase in the pH causes a further decrease in particle size with eventual nonformation of complexes. Interaction and stability studies of the complexes were done using photon correlation spectroscopy. The overall interaction appears to be a combination of hydrophobic interaction and hydrogen bonding. This has given rise to a unique ratio which we have called the [oxyphobic]/[oxyphilic] ratio or OOR. The interaction was found to depend on the molar ratio between poloxamer surfactants and PPA; the [O]_total/[-COOH] ratio; the size of the PPO hydrophobe, and the pH of the reaction mixture. pH measurement studies of these mixtures also gave similar results.     

Sorption of Water Vapor by Gelatin-Based Polymers: Estimation of Rate and Degree of Sorption Using the Spin-Probe Method

Moscow University Chemistry Bulletin - The spin-probe method is applied to estimate the rate and degree of sorption of water vapor by gelatin-based polymers. The rate and the sorption degree of...     

Photopolymerized Cellulose Acetate/Poly(Acrylic Acid) Semi-IPN Films for Wound Dressing Applications

In this work, semi-IPN films, composed of cellulose acetate(CA) and crosslinked poly(acrylic acid), have been synthesized via benzophenone (BP) induced free radical photo-polymerization of acrylic acid (AAc) in the presence of dissolved cellulose acetate (CA) using N,N’ methylene bisacrylamise (MB) as the crosslinking agent. The mechanical properties were tested for the films having different compositions of MB, CA and AAc in the feed mixtures. The tensile strength (TS) and percent elongation (PE) were found to increase with a concentration of CA in the films, but showed decreasing trends with concentrations of CA in the films. However, with AAc content in the films, the TS increased and PE showed just the opposite trend. The film samples were also studied for water vapor and oxygen permeation studies. The water vapor transmission rate (WVTR) decreased with MB and CA contents, but showed an increasing trend with AAc contents in the films. Finally, a representative sample showed fair antibacterial and antifungal action against E. coli and Aspergillus flavus when studied using the ‘Zone of inhibition method’.     

Stable Poly(Acrylic Acid) Films from Acrylic Acid/Argon Plasmas: Influence of the Mixture Composition and the Reactor Geometry on the Thin Films Chemical Structures

Thin films from acrylic acid and Ar mixtures were deposited on polypropylene films, aluminum foils and silicon 100 wafers by radiofrequency (RF) plasma polymerization. Different deposition conditions were investigated, varying the gas-mixture feed composition and the reactor geometry. For every tested condition, stable coatings (as assessed by long time immersion in phosphate buffer saline) were obtained by varying the RF power input. The influence of the gas carrier on the layer stability was discussed. The films were further characterized by water contact angle measurements, attenuated total reflectance infrared spectroscopy, X-ray photoelectron spectroscopy and atomic force microscope. Moreover, retention of carboxylic acid groups in the stable layers were investigated by means of ion-exchange reaction with thionin acetate. Results show a strong influence of the gas feed composition and the reactor geometry on the chemical structure of the deposited coatings, especially in their carboxylic groups concentration.     

Biotin-Conjugated Poly(Acrylic Acid)-Grafted Ultrasmall Gadolinium Oxide Nanoparticles for Enhanced Tumor Imaging

Herein, biotin (Bio)-conjugated poly(acrylic acid) (PAA)-grafted ultrasmall gadolinium oxide nanoparticles (Bio-PAA-Gd₂O₃ NPs) were synthesized for enhanced tumor imaging using Bio as a tumor-targeting ligand. The average particle diameter of Gd₂O₃ NPs was 2.1 nm. The Bio-PAA-Gd₂O₃ NPs exhibited excellent colloidal stability (i. e., no precipitation) and a high longitudinal water proton spin relaxivity (r₁) of 23.8 s⁻¹ mM⁻¹ (r₂/r₁=1.6 and r₂=transverse water proton spin relaxivity), which was ∼6 times higher than those of commercial Gd-chelated magnetic resonance imaging (MRI) contrast agents. Cytotoxicity tests using two cell lines showed that the Bio-PAA-Gd₂O₃ NPs were almost non-toxic up to the measured concentration of 500 μM Gd. The enhanced tumor imaging of the Bio-PAA-Gd₂O₃ NPs was demonstrated through their higher positive contrasts and longer contrast retention at the tumor after intravenous injection in T₁ MR images, compared with those of the control PAA-Gd₂O₃ NPs.     

Preparation of Poly(acrylic acid) Nano-films by In-situ Polymerization of Acrylic Acid Macroclusters on Silicon Oxide Surfaces

A new method for preparing poly(acrylic acid) (PAA) films on silicon oxide surfaces with smooth morphology has been developed. Acrylic acid (AA) was preferably adsorbed on silicon oxide surfaces in AA/ chloroform binary liquids and formed a hydrogen-bonded organized structure, which was called molecular macrocluster. AA macroclusters on silicon oxide surfaces were in-situ polymerized to obtain molecularly flat polymer films with thickness up to 10 nm. In-situ polymerizations were conducted by photo-irradiation in the presence of a photo initiator, 2,2-dimethoxy-2-phenylacetophenone (DPA). As a reference, the adsorption of PAA polymerized in the bulk solution was examined on silicon oxide surfaces. A series of techniques such as attenuated total reflection–FTIR (ATR-FTIR) spectroscopy, ellipsometry and atomic force microscopy (AFM) was utilized for characterizing two types of films. It was found that flat PAA films with linear hydrogen-bonded COOH could only be obtained by in-situ polymerization, which demonstrated this method was an effective way for preparing molecularly uniform polymer films. The surface morphology and thickness of obtained PAA films were found to be dependent on the monomer concentration, initiator amount and photoirradiation time. Molecularly uniform and flat PAA films were obtained after 5 min irradiation at 0.8 mol% AA in the presence of 5 wt% DPA.