聚4-乙烯基吡啶的合成与表征

以过氧化二苯甲酰(BPO)为引发剂,用悬浮聚合的方法制备了较高相对分子质量的聚4 乙烯基吡啶(P4VP)。通过对聚合产物相对分子质量测试结果的分析,研究了单体与水的体积比、引发剂用量、分散剂用量、反应时间、反应温度、搅拌速度等因素对4 VP聚合反应的影响。结果表明,聚合时间为1h、聚合温度为60℃、引发剂的质量分数(占单体量)为0.8%左右、分散剂的质量分数(占单体量)为0.6%、搅拌速度为300r/min时,P4VP的重均分子量就能达到6×105～9×105。另外,采用紫外吸收光谱(UV)、红外吸收光谱(IR)、核磁共振氢谱(1H NMR)、核磁共振碳谱(13C NMR)、热重 差热分析(TG DTA)等测试手段研究了P4VP的结构和性能。     

Synthesis and characterization of ruthenium complexes immobilized on poly(4-vinylpyridine)

The [Ru(NH₃)₅(H₂O)]²⁺ andtrans-[Ru(NH₃)₄SO₂(H₂O)]²⁺ complexes ions were immobilized on poly(4-vinylpyridine) (4-PVP) through reactions in aqueous solutions. The stability of the imobilized complexes was checked in aqueous solution in the pH 2.0–8.0 range. The number of pyridinic nitrogens in the polymer 4-PVP is 2.80±0.05 mmol/g according to nitrogen elemental analysis. Potentiometric titration experiments showed that the accessible nitrogen, in aqueous medium, was 0.94±0.02 mmol/g with a pK _a value of 7.4±0.2. In addition, ruthenium and sulfate analysis has demonstrated that about 15% of the accessible nitrogen sites are able to coordinate to the metal centers. The characterization of the immobilized complexes was made through diffuse electronic and infrared spectroscopies and differential pulse and cyclic voltammetries.     

pH及温度敏感性N-异丙基丙烯酰胺-丙烯酸共聚微凝胶的制备与表征

通过无皂乳液聚合得到了N-异丙基丙烯酰胺和丙烯酸的无规共聚物微凝胶,用电导仪测定了该微凝胶的表面羧基含量,用分光光度计测定了水凝胶溶液透光率在不同pH值和温度条件下的变化。结果表明,该微凝胶表面羧基含量随着聚合反应中丙烯酸质量分数的增加而增大;微凝胶表面羧基含量直接影响微凝胶的环境敏感性。     

Preparation and characterization of cationic copolymer latex. 1. Emulsion copolymerization of styrene with 4-vinylpyridine in the presence of non-ionic emulsifier

A study was made of the effect of 4-vinylpyridine (VP) on the kinetics of the emulsion polymerization of styrene (St) and on the distribution of polymeric VP in the cationic latex. Bimodal distribution of particle diameter was obtained in the polymerization under the conditions of low emulsifier concentration and high VP fraction in monomer feed. This would be caused by insufficient stabilization of resulting particles and by some changes in the character of growing radicals in aqueous phase with conversion. Polymerization under acidic conditions was affected by the amphiphilicity of VP-rich radicals which depended on VP fraction in monomer feed. On the surface of the latex particles prepared at pH 2 polymeric VP located preferentially whereas the latex particles prepared at pH 11 had a nearly statistical distribution of VP on their surface.     

Structure analysis of conductive polymer systems: Poly-4-vinylpyridine and poly(butadiene-b-4-vinylpyridine) with 7,7′,8,8′-tetracyanoquinodimethane

Summary The structure analysis of two conductive polymer systems-poly-4-vinylpyridine and poly(butadiene-b-4-vinylpyridine) with 7,7′,8,8′-tetracyanoquinodimethane (TCNQ)-was done by X-ray diffraction, scanning tunneling microscopy (STM) and FTIR. The charge transfer complex formed between the pyridine group and the known electron acceptor, TCNQ, is supposed to be the conductive element in these systems. In order to understand the structure of this complex, a model compound, the complex of 4-ethylpyridine (4EP) with TCNQ, 4EP/TCNQ₂, was studied by the mentioned methods. It appears that there are two crystalline modifications of the model compound with different type of stacks of the TCNQ molecules. In polymer systems only one type of the complex is dominant as revealed by joint analysis of X-ray diffraction diagrams, STM and FTIR data. In the STM image of the polymer surface one can distinguish that molecular stacks with periodicities of 4.1 ? in a row are separated (12.5?) from each other. Such organization is similiar to the one observed in conductive charge transfer complexes such as tetrathiofulvalene (TTF) with TCNQ. The ordered molecular domains are scattered on the polymer surface and take part in the formation of the conductive network.     

Characterization and catalytic performance of poly(4-vinylpyridine) supported on mesoporous carbon: comparison with poly(4-vinylpyridine) supported on mesoporous silica

In this study, the synthesis of poly(4-vinylpyridine) (P4VP) supported on mesoporous carbon (CMK-3) by in situ polymerization of 4-vinylpyridine in the presence of CMK-3 has been investigated. The structural properties of the P4VP/CMK-3 were investigated by FT-IR, XRD, BET, TGA, SEM and TEM techniques. The catalytic activity of this new heterogeneous basic catalyst was tested for Knoevenagel reaction. Excellent yields at room temperature in aqueous media and solvent-free conditions were obtained. The catalytic activity of this purely organic hybrid catalyst was compared with P4VP/SBA-15 to clarify the advantages of mesoporous carbon on mesoporous silica as support. The results showed that the stability of P4VP/CMK-3 was excellent and could be reused 10 times without much loss of activity in Knoevenagel reaction. Surprisingly, the composite prepared by mesoporous carbon showed much higher activity than that of P4VP/SBA-15. This unique result opens new perspectives for application of mesoporous carbons as structurally defined hydrophobic catalyst support in catalytic reactions.     

Redispersible dried hydroxyapatite particles with grafted pH-sensitivity polymer brushes of poly(styrene-co-4-vinylpyridine)

Reversible aggregation-redispersion transition of colloidal particles is of considerable importance in colloidal science and various industrial fields. In the present study, stimuli-responsive hybrid hydroxyapatite (HA) particles were prepared with redispersible ability in aqueous solutions even after separation from the “as synthesized” state and subsequent dry heat treatment. We firstly modified HA particles with sodium oleate as chelating agent, then introduced bromoalkyl functional groups through an addition reaction of unsaturated oleate molecule with bromine, and finally grafted polymer brushes of polystyrene-co-4-vinylpyridine onto HA. It was the pH-sensitive polymer shell that had rendered HA particles the redispersible ability, which was attributed to the protonation of the pyridine blocks in acidic solutions. The reversible dispersion-aggregation transition of HA could be controlled by alternating the pH value of aqueous solution. Protonated pyridine blocks had provided enough electrostatic and steric repulsions for colloidal HA to avoid effective collision.     

Thermal properties of novel supramolecular polymer networks based on poly(4-vinylpyridine) and disulfonic acids

Novel supramolecular polymer networks were prepared by the reaction of poly(4-vinylpyridine) (P4VP) with 1,5-naphthalenedisulfonic acid (NDS), 1,3-propanedisulfonic acid (PDS), or adipic acid (AA). The IR and XPS analyses of the polymer networks revealed that the P4VP/NDS complex has a higher ionic interaction between pyridinium cation and sulfonate anion than the P4VP/PDS complex, and that hydrogen bonding interaction between pyridine and carboxylic acid predominantly contributes for the P4VP/AA complex. When the glass transition temperatures of P4VP and P4VP/proton donor (1/1) complexes are compared, the higher order was P4VP/NDS>P4VP/PDS>P4VP>P4VP/AA, in agreement with a higher degree of ionic interaction. The P4VP/PDS complex had a melting endothermic peak in the DSC thermograms, which was not observed for the P4VP/NDS complex. The thermal decomposition temperature of the P4VP complexes is also investigated in relation to the intermolecular interaction.     

Interpenetrating polymer networks of poly(dimethylsiloxane): 1. Preparation and characterization

Model networks of ,ω-dihydroxy-poly(dimethylsiloxane) (PDMS) were prepared by tetrafunctional crosslinking agent tetraethyl orthosilicate (TEOS) and the catalyst stannous 2-ethylhexanoate. Hydroxylterminated chains of PDMS having molecular weights 15 × 10³ and 75 × 10³ g mol⁻¹ were used in the crosslinking reaction. Bimodal networks were obtained from a 50% (w/w) mixture of PDMS chains with M_n = 15 × 10³ and 75 × 10³ g mol⁻¹. A sequential interpenetrating network of these PDMS chains was also prepared. Physical properties of the elastomers were determined by stress-strain tests, swelling and extraction experiments, and differential scanning calorimetry measurements.     

Studies of chitosan. I. Preparation and characterization of chitosan/poly(vinyl alcohol) blend films

Various blending ratios of chitosan/poly (vinyl alcohol) (CS/PVA) blend films were prepared by solution blend method in this study. The thermal properties and chemical structure characterization of the CS/PVA blend films were examined by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and Fourier transform infrared (FTIR). Based upon the observation on the DSC thermal analysis, the melting point of PVA is decreased when the amount of CS in the blend film is increased. The FTIR absorption characteristic is changed when the amount of CS in the blend film is varied. Results of X‐ray diffraction (XRD) analysis indicate that the intensity of diffraction peak at 19° of PVA becomes lower and broader with increasing the amount of CS in the CS/PVA blend film. This trend illustrates that the existence of CS decreases the crystallinity of PVA. Although both PVA and CS are hydrophilic biodegradable polymers, the results of water contact angle measurement are still shown as high as 68° and 83° for PVA and for CS films, respectively. A minimum water contact angle (56°) was observed when the blend film contains 50 wt % CS. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Studies of crosslinked poly(AM-MSAS-AA) gels. I. Synthesis and characterization

Novel superabsorbent copolymers were prepared from acrylamide (AM), sodium methallylsulfonate (MSAS), sodium acrylate (AA), and N,N′-methylenebisacrylamide (BisA) in aqueous solution using potassium persulfate (KPS)/N,N,N′,N′-tetramethylethylenediamine (TMEDA) as the redox initiator. The copolymers were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The experimental results show that absorbency increases with an increase in crosslinker concentration but decreases with excessive crosslinking. The ionic groups in the polymer network significantly increase the equilibrium swelling. Water retention at pressures of 1–10 kg/cm² and temperatures of 60 and 100°C are also reported. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1001–1007, 1997     

聚(N-异丙基丙烯酰胺)/聚丙烯酸半互穿网络微凝胶的合成及表征

利用IPN技术合成了一种具有温度和pH双重敏感性的聚（N-异丙基丙烯酰胺）/聚丙烯酸半互穿网络微凝胶（PNIPAM/PAAc semi-IPN）。这种微凝胶在酸性条件下发生典型的体积相转变;而在弱碱性条件下,当温度低于聚（N-异丙基丙烯酰胺）（PNIPAM）微凝胶的体积相转变温度（VPTT）时,微凝胶的粒径随着温度的上升而增大,当温度达到VPTT后,粒径突然急剧减小,并随着温度的逐渐上升而减小,最终趋向平衡。     

Pervaporation of nonaqueous ethanol azeotropes through interpenetrating polymer network membranes prepared from poly(4-vinylpyridine) and poly(vinyl alcohol)

Highly hydrophilic interpenetrating polymer network (IPN) membranes were prepared from a mixture system of poly(4-vinylpyridine) (P4VP) and poly(vinyl alcohol) (PVA) by quaternizing crosslinking of P4VP with 1,4-dibromobutane (DBB) and simultaneous crosslinking of PVA with hexamethylene diisocyanate (HMDI). The membrane performance in pervaporation (PV) for the azeotropic mixture of ethanol with a less polar organic liquid (chloroform, benzene, carbon tetrachloride, and cyclohexane) was investigated. The strength of these IPN membranes was higher than that of the cellulose acetate membrane and depended on the membrane composition. All the membranes were ethanol permselective for the azeotropic feeds and equimolar mixture feeds as well. Only the swelling degree Q of the membrane, among several physicochemical factors, showed a relationship with the separation performance for the four feeds; a lower value of Q generally corresponded to a higher separation factor and smaller permeability. The membrane composition, which exhibited an optimum membrane performance, was examined in detail for some membranes. Both the separation factor for sorption and that for diffusion far exceeded unity, but the latter was greater in most cases than was the former and dominated the overall separation. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2729–2738, 2001     

Microwave assisted quaternization of poly(4-vinylpyridine) with 1-bromohexane

Quaternization reaction is a well-known technique and can be applied to obtain functional polycations. If quaternization agents used in this reaction contain more than 4 carbons, it can take days or weeks to reach high degrees in quaternization. In the study, microwave heating was used to increase the reaction rate. Kinetics of microwave-assisted quaternization of poly(4-vinylpyridine) with 1-bromohexane was investigated by varying the reaction conditions, such as solvent, temperature, molar ratio of components and concentrations. In less than 1 h, quaternization degree of poly(4-vinylpyridine) reached higher than 80% values in DMF and DMSO with microwave heating at 80 °C. Higher polymer concentration and molar ratio of N_{1-bromohexane}/N_{4-vinylpyridine} also increased the reaction rate. It was demonstrated that microwave heating can be applied to increase the quaternization reaction rate. Very short reaction times as low as minutes may allow quaternization reaction to be used in more studies for novel functional polycations.     

Pervaporation and solute separation through semi-interpenetrating and interpenetrating polymer network membranes prepared from poly(4-vinylpyridine) and poly(glycidyl methacrylate)

Semi-interpenetrating (SPN) and interpenetrating polymer network (IPN) membranes were prepared from a mixture system of poly(4-vinylpyridine) (P4VP) and poly(glycidyl methacrylate) (PGMA) by quaternizing crosslinking of P4VP with 1,4-dibromobutane (DBB) and by simultaneous crosslinking of P4VP with DBB and PGMA with tetraethylenepentamine (TEPA), respectively. The difference between SPN and IPN was demonstrated by IR, tensile strength, and dimension stability. The membrane performance in pervaporation (PV) for ethanol–water mixtures and reverse osmosis (RO) was investigated. The polymer mixture of 1 : 1 on a monomer base with 30 mol % DBB on the 4VP unit and 5.6–7.5 mol % (8–10 wt %) TEPA on the GMA unit gave an optimum membrane performance. Those crosslinked membranes were stronger than was the cellulose acetate membrane, mostly owing to the PGMA chains, and exhibited a high separation factor for the azeotropic feed in PV. IPN membranes generally showed a performance higher than that of the SPN ones. An attempt to improve the product rate was made by the addition of a water-soluble polymer to the membrane on casting. The separation factor for solubility in the membrane at the feed side dominated the overall separation factor, particularly for feeds of higher ethanol concentrations. © 1998 John Wiley & Sons, Inc. J Appl Polm Sci 69: 1953–1963, 1998     

Electropolymerized poly(2-vinylpyridine) coatings as ion-exchange polymer modified electrodes

The effects of pH and of the nature and concentration of the electrolyte on the electrochemical behaviour of the Fe(CN)^3–/4– ₆ charge-transfer reaction at a poly(2-vinylpyridine)-coated electrode formed by electropolymerization have been studied. Cyclic voltammetry during the Fe(CN)^3– ₆ incorporation process was combined with measurement of the saturated concentration of the Fe(CN)^3– ₆ confined in the films to investigate the electrochemical behaviour and the fundamental nature of the ion-exchange polymers. The poly(2-vinylpyridine) films formed by electropolymerization were found to have better properties (i.e., larger amount of Fe(CN)^3– ₆ can be incorporated at various pH values and films are more chemically stable under acidic conditions) as polymer-modified electrodes than those formed by solvent evaporation. Of the various anions studied, ClO^– ₄ was found to be distinct from the others (Cl^–, NO^– ₃, Br^– and SO^2– ₄). On the one hand, the polymer films exposed to ClO^– ₄ are more dense and rigid than those exposed to other anions and show relatively little electroactivity. On the other hand, when the films are exposed to increasing concentrations of Cl^–, the films become more swollen, thereby reducing the resistance within the film and enhancing the rate of charge-transfer from the outer film surface to the electrode surface.     

Graft copolymers: 1. Synthesis and characterization of poly(styrene-g-2-vinylpyridine)

A method of synthesizing poly(styrene-g-2-vinylpyridine) graft copolymers has been perfected. Attempts involving carbanionic initiation from partly metallated poly(p-bromostyrene) have not given the expected results. On the other hand, carbanionic deactivation of monofunctional living poly(2-vinylpyridine) on partly chloromethylated polystyrene has allowed us to obtain the expected graft copolymers. Several features have been examined: the influence of the grafting reaction on the way in which mixing of parent homopolymers is achieved; the effects of the nature of the counterion and temperature and the influence of different parameters on the yield of grafting and the problem of the elimination of the ungrafted homopolymer. No side reaction is observed at the time of grafting. Careful characterization of the resulting products shows they present a narrow molecular weight distribution, they are homogeneous in chemical composition, their structure is well defined with respect to the length of the backbone, and the number and the length of grafts; in addition the architecture of the graft molecule can be predicted.     

Miscible blends of poly(vinyl phenyl ketone hydrogenated) and poly(styrene-co-4-vinylpyridine)

Miscibility behavior over a wide composition range was detected for polymer blends of poly(vinyl phenyl ketone hydrogenated) (PVPhKH) with poly(styrene-co-4-vinylpyridine) (PS-co-4VPy). Differential scanning calorimetry (DSC) and thermo mechanical analysis (TMA) reveal that each composition has only one glass transition temperature. The variation of the glass transition temperature with composition for PVPhKH/PS-co-4VPy miscible blends follows the Gordon-Taylor equation. FTIR analysis of this binary system indicates the existence of hydrogen bonding between pyridine ring of PS-co-4VPy and hydroxyl groups insert into PVPhKH. This specific interaction has a decisive influence in the phase behavior of PVPhKH/PS-co-4VPy blends.     

Morphology control of a poly(styrene-b-butadiene-b-4-vinylpyridine) ABC three-block polymer by binary solvent casting

Casting of a poly(styrene-b-butadiene-b-4-vinylpyridine) ABC three-block polymer from binary solvent systems was carried out to control the microphase-separated structure. Various morphologies including a ball-in-a-box structure and a lamellar structure were observed. On the basis of the change in solvent composition during the casting process, we deduced that the former structure was formed where the selective solvent for poly(4-vinylpyridine) in the binary mixture was lost by vaporization in an early stage of casting. On the contrary, the latter structure was formed under a casting condition when solvents were equally distributed into the three phases and/or the distribution and the composition of solvents had not varied significantly during the casting process. If casting proceeds from an opaque solution in which some aggregates already exist, or if the selective solvent for one or two of the three block segments vaporizes faster than other solvent in an early stage of casting, the morphology becomes a random and indefinite structure.     

Moisture sorption of polyelectrolyte complex between poly(acrylic acid) and poly(4-vinylpyridine)

Successive differential sorptions have been measured for the system polyelectrolyte complex of poly(acrylic acid)/poly(4-vinylpyridine) + water vapor. The sorption data revealed that the sorption process of water vapor in the complex is controlled not only by diffusion mechanism but also by relaxation mechanism of polymer chains. It has been considered that the complex is composed of a loosely crosslinked, slightly ionized, and relatively homogeneous network structure. The sorption–desorption kinetics have also been investigated for the region of intermediate and high vapor pressures. The interval sorption–desorption curves demonstrated that the complex has the nature of the hysteresis effect in sorptions. It has been concluded that the appearance of sorption hysteresis is due to the depression of mobility of polymer chains resulting from crosslinks between carboxyl groups and pyridine rings.