微波辐射用于聚合反应的研究进展

微波辐射在高分子化学研究领域中的应用越来越广泛 ,效果也十分明显 ,与常规加热方式相比 ,微波辐射具有缩短反应时间 ,提高反应产率 ,节省能源损耗 ,制得产物性能好等优点。近年来 ,微波辐射在聚合反应中的应用也越来越多。因此本文对微波辐射在高分子聚合反应中的应用研究进行了综述。     

Quantification of Polymer Fouling on Heat Transfer Surfaces During Synthesis

During the synthesis and processing of polymers, a significant amount of polymer may be deposited on the heat transfer surfaces. This deposit is unwanted and is usually named fouling. This study deals with the fouling behavior of a vinyl acetate/vinyl ester copolymer during emulsion polymerization and compares this to fouling of an already reacted vinyl acetate/ethylene copolymer dispersion. Besides the state of polymerization, also the influence of the wall temperature is investigated. The experiments are performed on cooled and heated surfaces. The deposition process is quantified by the mass‐based fouling resistance, the height of the fouling layer, and the surface coverage using a digital microscope. It is found that the state of polymerization and the temperature gradient between wall and bulk exert a strong influence on the fouling behavior, especially on the structure of the fouling layer.     

Towards bilirubin imprinted poly(methacrylic acid-co-ethylene glycol dimethylacrylate) for the specific binding of α-bilirubin

With α-bilirubin as a molecular template, polymerization of methacrylic acid (MAA) was carried out with the aid of the initiator 2,2-azobisisobutyronitrile (AIBN) and the cross-linking agent ethylene glycol dimethylacrylate (EGDMA). Bulk polymerization was successfully carried out so that poly(methacrylic acid-co-ethylene glycol dimethylacrylate) (poly(MAA-EGDMA)) imprinted with α-bilirubin was first developed. UV irradiation polymerization and heated polymerization methods were compared. Effect of different ratios of monomer to EGDMA during the polymerization was also discussed. Proper solvent for better desorption of α-bilirubin from the imprinted poly(MAA-EGDMA) was investigated. In addition, SEM photos were provided for observing the differences between the surfaces of the imprinted poly(MAA-EGDMA) before and after extraction. The corresponding binding results of α-bilirubin imprinted poly(MAA-EGDMA) and non-imprinted poly(MAA-EGDMA) both after extraction were compared. How the pH values during extraction stage affected the binding capacities of the imprinted polymer as well as non-imprinted polymer were also discussed. Similar study and comparison were made for different binding pH values. Different compounds of similar molecular weight were used to show the specific binding of the imprinted polymer for bilirubin. The results further confirmed the successful binding as well as specificity of the imprinted poly(MAA-EGDMA) for α-bilirubin.     

A differential scanning calorimeter study of the crystal forms and polymerization kinetics of 2,4-hexadiynyl-1,6-bis(p-toluenesulfonate)

The thermal properties of 2,4-hexadiynyl-1,6-bis(p-toluenesulfonate) have been explored by program temperature and isothermal differential calorimetry. The heat of fusion for the rapidly heated pure solid was 8254 cal/mole (34,540 J/mole) at 367.1°K (93.8°C). This amounts to an entropy change of 22.5 cal/mole °K (94.1 J/mole °K). The energy of activation for the thermal polymerizations was 18.97 kcal/mole (79.37 kJ/mole). The thermal polymerization appears to follow a solid–solid phase transition which proceeds by random homogeneous nucleation throughout the process. The kinetics were simple first order over 70% of the reaction. Programmed temperature studies indicate that during the first 10% of the polymerization a new high temperature (mp 375.4°K) solid phase is formed which acts as the monomer form during the bulk of the reaction.     

Kinetics of DC Discharge Plasma Polymerization of Hexamethyldisiloxane and Pyrrole

This paper investigates DC plasma polymerization kinetics by combining plasma parameters with film deposition rate in different conditions. The monomers hexamethyldisiloxane (HMDSO) and pyrrole were used. Both single and double Langmuir probes were used to measure the plasma parameters in pulsed power and continuous discharges. In order to avoid probe tip contamination, the probe was heated. Plasma density and electron temperature are reported. The electron current wave form is obtained in pulse power conditions. From the data, a plasma polymerization model is proposed. The conclusion is that the monomer molecules and free radicals adsorbed on the substrate surface react with activated sites produced by high energy ions bombarding the film, resulting in polymerization at the film surface.     

A study of post-radiation polymerization of 2-hydroxyethyl methacrylate γ-irradiated in crystalline and vitreous states

Dependent on the mode of preparation, 2-hydroxyethyl methacrylate (HEMA) can at low temperatures acquire either vitreous or crystalline states. On heating γ-irradiated vitreous HEMA, polymerization starts immediately after transition of the system from the vitreous state to that of a supercooled liquid (T_g = 177 K). This provides conditions for growth of polymer chains and suppression of bimolecular termination of active growing centres. Polymerization of radiated crystalline HEMA occurs at higher temperatures in the monomer melting region. At equal dosages of preliminary radiation, the transformation depth for the crystalline sample is considerably lower than that for the vitreous sample; this effect is due to different molecular mobilities in heated crystalline and vitreous samples. In HEMA post-polymerization, the very early transformation stages yielded an insoluble cross-linked polymer. This paper discusses the possible mechanism of cross-linking during polymerization of monomers of the HEMA type as a result of detachment of hydrogen from the carbon atom in the glycol group.     

Solid-state reactions of vinylpyridine coordination complexes. II

Crystals of the trans-octahedral complex Co(4-Vpy)₄(NCS)₂ on being heated below the melting point decompose with liberation of 4-vinylpyridine (Vpy) and concurrent polymerization of the free monomer. The two reactions have been followed by differential scanning calorimetry, thermogravimetry, and optical microscopy. Polymerization is inhibited by inclusion of hydroquinone during recrystallization of the complex. This has allowed the kinetic analysis of the decomposition and polymerization to be simplified. Isothermal mass-loss determinations under reduced pressure (10^?2 torr), at various temperatures in the range 120–160°C, on hydroquinone-inhibited crystals corresponded to the loss of up to three molecules of vinylpyridine per molecule of starting complex. With uninhibited crystals over the same temperature range the total number of ligands lost was approximately two with a marked decrease near 175°C owing to rapid polymerization. Isothermal decomposition curves for inhibited and uninhibited crystals approximated to the Avrami-Erofeev equation. Values of n varied with temperature. Activation energies for decomposition and polymerization for both types of crystal were estimated from Arrhenius plots.     

Controlled‐synthesis of Slightly Crosslinked Poly(dimethyldiallylammonium chloride)s Used as Useful Polycationic Dye‐fixatives on Cotton Fabric

A series of slightly crosslinked poly (dimethyldiallylammonium chloride) s (PDMs) as useful polycationic dye‐fixatives on cotton fabric were synthesized by copolymerization of triallylmethylammonium chloride (TAMAC) and dimethyldiallylammonium chloride (DM). The structures of slightly crosslinked PDMs could be controlled by varying molar ratio of TAMAC to DM during polymerization, and their molecular weights were possibly controlled by adjusting different polymerization conditions. The results showed, under the same conditions that the polymerization temperatures were kept at 65 °C for 6 h and then heated to 80 °C for 2 h, when the initial monomer concentrations (w/w) were increased from 37% to 50%, the initiator amount were gradually decreased from 9% to 5%, a series of slightly crosslinked PDMs with controlled structures of 1%‐5% TAMAC molar contents and controlled intrinsic viscosities of 0.18～0.65 dL/g were successfully synthesized, which were as designed and could be expected as novel useful polycationic dye‐fixatives on cotton fabric.     

Polymerization of cyclic ethers in the presence of maleic anhydride. Part II. Investigation of the polymerization mechanism

In order to elucidate the reaction mechanism of both the radiation-induced and benzoyl peroxide-catalyzed polymerizations of cyclic ethers in the presence of maleic anhydride, the development of color during reaction and copolymerization of oxetane derivatives were investigated. Upon addition of a small amount of the γ-ray or ultraviolet-irradiated equimolar solution of a cyclic ether and maleic anhydride to isobutyl vinyl ether, a rapid polymerization took place, and the resulting polymer was confirmed to be a homopolymer of isobutyl vinyl ether. A heated solution of dioxane, maleic anhydride, and a small amount of benzoyl peroxide can initiate the polymerization of isobutyl vinyl ether in the same manner. The electrical conductivity of a 1:1 mixture of maleic anhydride and dioxane is increased by about a factor of ten after ultraviolet irradiation. These results indicate that some cationic species are actually formed in the system by irradiation or the decomposition of added benzoyl peroxide. The mechanism of formation of the cationic species responsible for the initiation may be explained as follows. A free radical of an ether is formed by abstraction of a hydrogen atom attached to the carbon adjacent to oxygen atom, followed by a one-electron transfer from the resulting radical to maleic anhydride, an electron acceptor, to yield the cationic species of the ether and the anion-radical of maleic anhydride, respectively. The resulting cationic species as well as the counteranion-radical are resonance-stabilized. Therefore, the present polymerization may be designated a radical-induced cationic polymerization.     

Cyclopolycondensations

Fully aromatic polyquinazolinediones of high molecular weight were prepared by the cyclopolycondensation reaction of 4,4′-diamino-3,3′-biphenyldicarboxylic acid with aromatic diisocyanates. The poly(phosphoric acid) solution polymerization techniques yielded tractable poly(urea acid), which was converted to polyquinazolinediones by thermal cyclodehydration at 300–400°C. under reduced pressure. The polyquinazolinediones thus obtained have excellent thermal stability both in nitrogen and in air. The poly(urea acid) is soluble in dimethyl sulfoxide, and films can be cast from the polymer solution of poly(urea acid) (η_inh = 0.8 to 1.8). The films are made tough by being heated in nitrogen or under reduced pressure at 300–400°C. The polymerization mechanism of the cyclopolycondensation reaction was studied, and it was established that the polymerization proceeded through the formation of tractable poly(urea acid), Structure (I), of high molecular weight, followed by cyclodehydration, yielding poly(1,2-dihydro-2-imino-4H-3,1-benzoxazin-4-one), Structure (II). On subsequently being heated this undergoes intramolecular rearrangement along the polymer chain, giving the thermodynamically stable polyquinazolinedione, Structure (III).     

环硅氧烷负离子乳液聚合中活性中心浓度的变化规律

以八甲基环四硅氧烷(D4)为单体,十二烷基二甲基苄基氢氧化铵(BDAH)为乳化剂兼催化剂,进行环硅氧烷负离子乳液聚合,采用凝胶色谱(GPC)测定聚合产物的转化率及分子量.在此基础上,分析基元反应,提出活性中心生成机理,并应用环硅氧烷开环聚合普适动力学模型计算乳液聚合平衡之前的活性中心浓度变化规律.结果发现,聚合温度较低时,活性中心浓度随时间逐渐增加,最终恒定;聚合温度较高时,活性中心浓度随时间仅单调递增.结果与机理相符.     

Large uniform-sized polymer beads for use as solid-phase supports prepared by ascension polymerization

Large uniform-sized polymer beads are desirable for "one-bead-one-compound" applications in the combinatorial synthesis of compound libraries. We have developed a technique for the preparation of large polymer spheres with narrow size distributions. Uniform-sized poly(styrene-co-divinylbenzene) beads with diameters in excess of 1 mm have been prepared by free radical polymerization in an ascension process through a heated column. The size of the beads can be adjusted by the diameter of the injection needle and the injection speed. The resin beads can be made porous by the incorporation of a porogen during the preparation; they reach a specific surface area in excess of 200 m(2)/g. The mechanical properties of the spheres and their use in organic synthesis have been studied.     

Cyclopolycondensation. XII. Polymerization mechanism of polybenzoxazinones in polyphosphoric acid medium

The polymerization mechanism of polyphosphoric acid (PPA) solution polymerization of an aromatic diaminodicarboxylic acid with aromatic dicarboxylic acid derivatives was studied. By means of NMR methods, the initiation process for the polymerization of polybenzoxazinone in PPA medium was elucidated. The NMR spectra of a series of compounds were taken, and the salt formation of amino groups of monomer with PPA and the equilibrium between the salt and the free amino group were determined. It was established that the polymerization proceeded through the formation of phosphorylated intermediates to give the salt of amino groups of monomer with PPA. In the second step, the amine–PPA salt dissociates into the free amino group and PPA at the polymerization temperature above 140°C. Polymerization proceeds through the attack of “free” amino on phosphorylated carbonyl compounds to form polyamide acid of high molecular weight, and on subsequently being heated in PPA at higher temperatures, it undergoes an intramolecular cyclodehydration along the polymer chain to form polybenzoxazinones.     

Controlled synthesis of novel reactive cationic copolymers of 3-chloro-2-hydroxypropylmethyldiallylammonium chloride and dimethyldiallylammonium chloride [P(CMDA-DMDAAC)s]: designed as useful polycationic dye-fixatives on cotton fabric

A series of novel reactive cationic copolymers [P(CMDA-DMDAAC)s] of 3-chloro-2-hydroxypropylmethyldiallylammonium chloride (CMDA) and dimethyldiallylammonium chloride (DMDAAC), were designed as useful polycationic dye-fixatives on cotton fabric. The structures of obtained P(CMDA-DMDAAC)s could be controlled by varying molar ratios of raw materials of CMDA to DMDAAC during polymerization, and their molecular weights were possibly controlled by adjusting different polymerization conditions. The results showed that under the same conditions when the polymerization temperatures were kept at 60 °C for 6 h and then heated to 70 °C for 2 h, when the initial monomer concentrations (w/w) were increased from 23 to 40 % and the initiator amounts were gradually decreased from 7 to 6 %, a series of novel products P(CMDA-DMDAAC)s with 2–20 % molar contents of reactive units (CMDA units) in main chains and controlled intrinsic viscosities of 0.15–0.76 dL/g were successfully synthesized, which were as designed and could be expected as novel useful reactive polycationic dye-fixatives on cotton fabric.     

聚[4-(4′-八甲基四硅氧基)二苯醚]分子量与特性粘数的关系

本工作对本体聚合的交替共聚物,聚[4-(4′-八甲基四硅氧基)二苯醚]作了重沉淀分级,再用粘度法、动态渗透压,光散射及GPC对级分和未分级试样作了分子量和分布宽度的测定。实验数据经多分散性改正后,得到该共聚物单分散的特性粘数-分子量关系式: [η]=2.33×10~(-3)M~(0.88)(毫升/克,25℃,四氢呋喃)该共聚物在四氢呋喃溶液中的第二维利系数A_2随分子量的增加而降低,依从A_2=3.60×10~(-2)的关系. 该共聚物在水中加热后放置几天会产生降解。紫外和红外光谱说明降解后共聚物的化学组成没有明显变化。     

Aqueous polymerization of methyl methacrylate catalyzed by copper metal and some of its compounds

The aqueous polymerization of methyl methacrylate (MMA) with sodium bisulfite as initiator was carried out in a nitrogen atmosphere with and without inorganic substances like copper metal, cupric and cuprous oxides, and cupric sulfide. It was also done in the presence of organocopper compounds like copper phthalocyanine and copper biphthalocyanine. The catalytic effect of these compounds was studied. Mildly heated cupric sulfide proved to have a small catalytic effect on the polymerization process that may be attributed to the retarding effect of the released elementary sulfur. The catalytic effect of the different copper compounds and the copper metal equivalent contained in them was studied. The polymerization process revealed that cuprous and cupric oxides possess the highest catalytic influence. An attempt was made to investigate the role of the different anions on the polymerization process. It was found that an increase on the concentration of the copper compounds leads to a corresponding increase in the catalytic effect. It was also observed that the behavior of insoluble copper catalysts is different from that of the soluble. The effect of these catalysts on the average molecular weight of the poly(methyl methacrylate) (PMMA) produced was also examined.     

New catalytic systems for the manufacture of poly(aspartic acid)

Aspartic acid (I), when heated to a temperature in excess of 180 °C, undergoes a solid-state condensation polymerization to afford the useful polymeric intermediate known as poly(succinimide) (II). Treatment of poly(succinimide) with aqueous base, such as sodium hydroxide, affords sodium poly(α,β-DL-aspartate) (III) also known as thermal poly(aspartate) (TPA). Acid catalysts, such as phosphoric acid have been added to the aspartic acid to afford higher-molecular-weight poly(succinimide) than is obtained in the non-catalyzed polymerization. Recently, new sulfur-based catalysts have been disclosed for the polymerization of aspartic acid. The sulfur-containing catalysts provide a route to highly biodegradable, low-color poly(aspartate)s in the molecular weight range of 2 000 to 20 000. A comparison of biodegradability, molecular weight, and spectral characteristics of the poly(succinimide)s and poly(aspartate)s derived from the catalyzed and non-catalyzed polymerizations is presented.     

Cyclopolycondensation. XIII. New synthetic route to fully aromatic poly(heterocyclic imides) with alternating repeating units

Fully aromatic poly(heterocyclic imides) of high molecular weight were prepared by the cyclopolycondensation reactions of aromatic diamines with new monomer adducts prepared by condensing orthodisubstituted aromatic diamines with chloroformyl phthalic anhydrides. The low-temperature solution polymerization techniques yielded tractable poly(amic acid), which was converted to poly(heterocyclic imides) by heat treatment to effect cyclodehydration at 250–400°C under reduced pressure. In this way, the polyaromatic imideheterocycles such as poly(benzoxazinone imides), poly(benzoxazole imides), poly(benzimidazole imides) and poly(benzothiazole imides) were prepared, which have excellent processability and thermal stability both in nitrogen and in air. The poly(amic acids) are soluble in such organic polar solvents as N,N-dimethyl-acetamide, N-methylpyrrolidone, and dimethyl sulfoxide, and the films can be cast from the polymer solution of poly(amic acids) (η_inh = 0.8–1.8). The film is made tough by being heated in nitrogen or under reduced pressure to effect cyclodehydration at 300–400°C. The polymerization was carried out by first isolating the monomer adducts, followed by polymerization with aromatic diamines. On subsequently being heated, the open-chain precursor, poly(amic acid), undergoes cyclodehydration along the polymer chain, giving the thermally stable ordered copolymers of the corresponding heterocyclic imide structure.     

Polymerization of vinyl compounds with heterocyclic groups. IV. Thermal polymerization of 2-vinylthiophene

2-Vinylthiophene was found to undergo thermal polymerization. With benzene as diluent, the overall rate of polymerization was proportional to the 2.5 power of monomer concentration, suggesting that the thermal initiation is a termolecular process. The following Arrhenius equation was obtained from the polymerization data for the range 55–100°C: The activation energy of the thermal initiation was estimated to be 28.2 kcal/mole, which was similar to those values obtained for styrene and 2-vinylfuran. When a dilute solution of the monomer in bromobenzene was heated in an ampoule at 151°C, a dimer, mp 82°C, was obtained in a good yield. The spectroscopic data indicated that the dimer was a Diels-Alder type adduct. The initiation of the thermal polymerization was considered to involve hydrogen abstraction by monomer from the Diels-Alder dimer, in common with the initiation of other vinylaromatic monomers.     

Methyl methacrylate-n-butyl methacrylate copolymer containing ferric chloride: Mössbauer study

Methyl methacrylate /MMA/-n-butyl methacrylate /nBuMA/ copolymer containing anhydrous ferric chloride was prepared by free radical polymerization at 70 °C. TGA studies showed that the addition of ferric chloride increases the thermal stability of copolymer by 90 °C. Mössbauer studies of the copolymer were carried out to determine the oxidation state and environments of iron in the copolymer. Mössbauer studies of the copolymer heated at 150 °C, 300 °C and 500 °C for 1 h showed that during the thermal degradation, no reduction of Fe³⁺ takes place.