Polymerization of 1,3,5-trithiane in the solid state initiated by UV-irradiation. I. Polymerization conditions and polymer characterization

The solid-state 1,3,5-trithiane polymerization initiated by UV-irradiation was studied at various irradiation times and various polymerization temperatures. The conversion of monomer to polymer reaches limiting values (at longest) in about 30 min of reaction. The apparent activation energy of this process is somewhat higher than in the chemically initiated polymerization. Generated by UV, active centers, which initiate the polymerization, are stable. On the basis of X-ray diffraction studies it was found that the prepared polythiomethylene has a hexagonal structure and high degree of crystallinity. In the polymer investigated, a new additional crystal phase is formed, which is not stable.     

Four-center type photopolymerization in the solid state. II. Polymerization mechanism of 2,5-distyrylpyrazine

The polymerization mechanism of trans,trans-2,5-distyrylpyrazine (DSP) has been investigated and some crystal changes along with the polymerization process have been observed through polarizing microscope and x-ray diffraction pattern. Information has been obtained on the active species, polymerization reaction type, and other factors such as light intensity, reaction temperature, or crystalline state. The polymerization of DSP occurs only in the solid state by photoirradiation. Reduced viscosity increases gradually with the increase of conversion and increases sharply above 80% conversion. Polymerization rate increases with the increase of light intensity and temperature. On the other hand, reduced viscosity decreases with the increase of temperature but does not depend on light intensity within the range investigated. The polymer obtained at low conversion as well as at high conversion has high crystallinity, and the direction of polymer axes is simply related to that of monomer crystal. It was concluded that the four-center type polymerization of DSP proceeds topochemically by a photochemically induced stepwise mechanism.     

Mechanism of the polymerization of trifluoroacetaldehyde initiated by azobisisobutyronitrile

The polymerization of fluoral initiated by the photolyzed decomposition of azobisisobutyronitrile at low temperature has been studied. Up to 2% conversion, the effect of radical scavengers and the order with respect to initiator and light intensity indicate that the reaction occurs by a conventional radical polymerization mechanism. At about 2% conversion autoacceleration sets in and the rates become irreproducible. This is explained by typical occlusion phenomena. Tracer studies show that polymer prepared at high conversion contains initiator fragments indicating that primary propagation is by monomer addition to radicals. The reaction mechanism is discussed.     

单电子转移活性自由基聚合制备支化聚丙烯酸甲酯的研究

以丙烯酸2-(2-溴异丁酰氧基)乙酯(BIEA)为引发剂单体(inimer),丙烯酸甲酯(MA)为单体,Cu0/CuBr2和N,N,N',N″,N″-五甲基二亚乙基三胺(PMDETA)为催化体系,二甲亚砜(DMSO)为溶剂,在常温(25℃)下通过单电子转移活性自由基聚合(SET-LRP)合成支化聚丙烯酸甲酯.聚合反应过程中,采用气相色谱(GC)、核磁共振(1H-NMR)和三检测体积排除色谱(TD-SEC)等测试手段跟踪分析和表征支化聚合物的结构.研究结果表明,采用SET-LRP方法,铜粉作为催化剂,常温下聚合反应就能快速进行,130 min之内MA的转化率已达99%以上,制备出高分子量支化聚合物.随着反应的不断进行,聚合物支化程度不断提高,相比较同分子量下的线型聚合物其黏度不断下降,Mark-Houwink特征常数α最小可达0.290.此外,低分子量聚合物组分随着反应不断减少,在高单体转化率下,聚合体系中以高支化度的聚丙烯酸甲酯为主.     

Solid-state polymerization of 1,2,3,4-diepoxybutane initiated by cobalt-60 γ-radiation

The solid-state polymerization of 1,2,3,4-diepoxybutane appears to proceed “insource” by an ionic mechanism and has an overall activation energy of 0.4 kcal./mole with an intensity dependency of 0.99. There is a rapid increase in the rate of polymerization just prior to the melting point and a very low rate for the liquid-phase reaction. Limiting conversions of 5% polymer are observed at ?196°C. for irradiation in vacuo. No limiting conversion was observed when the monomer was polymerized in the presence of air or in vacuo at ?78°C. Under all polymerization conditions the reactions were characterized by the absence of an induction period.     

Atom Transfer Radical Polymerization in the Solid-State

Poly(2-vinylnaphthalene) was synthesized in the solid-state by ball milling a mixture of the corresponding monomer, a Cu-based catalyst, and an activated haloalkane as the polymerization initiator. Various reaction conditions, including milling time, milling frequency and added reductant to accelerate the polymerization were optimized. Monomer conversion and the evolution of polymer molecular weight were monitored over time using ¹H NMR spectroscopy and size exclusion chromatography, respectively, and linear correlations were observed. While the polymer molecular weight was effectively tuned by changing the initial monomer-to-initiator ratio, the experimentally measured values were found to be lower than their theoretical values. The difference was attributed to premature mechanical decomposition and modeled to accurately account for the decrement. Random copolymers of two monomers with orthogonal solubilities, sodium styrene sulfonate and 2-vinylnaphthalene, were also synthesized in the solid-state. Inspection of the data revealed that the solid-state polymerization reaction was controlled, followed a mechanism similar to that described for solution-state atom transfer radical polymerizations, and may be used to prepare polymers that are inaccessible via solution-state methods.     

Thermal and radiation-induced polymerizations of N-tert-butylacrylamide and (N-tert-butylacrylamide)2–ZnCl2 complex

The thermal and radiation-induced in-source and postirradiation polymerizations of N-tert-butylacrylamide and (N-tert-butylacrylamide)₂–ZnCl₂ complex of this monomer were studied at various temperatures. In in-source, solid-state polymerizations of monomer and complex the conversion was about 95% at 21°C in about eight days. Their postirradiation polymerizations were also studied in solid state. The conversion-time curves of these two systems show an autoacceleration as in-source polymerization. In both types of polymerization the overall rate of polymerization of complex was higher than that of pure monomer at the same polymerization temperature. In investigations of the thermal polymerization of N-tert-butylacrylamide and ZnCl₂-complex it was observed that the ZnCl₂-complex system can be polymerized in air in the molten and solid state. The conversion of monomer to polymer reaches limiting values in solid state in about 1 hr. The thermal polymerization of ZnCl₂-complex in the molten state was also studied and 100% conversion was obtained in 30 min. The thermal polymerization of pure monomer was studied in vacuum and an appreciable amount of polymer was obtained in the molten state; however, the thermal polymerization of this monomer is negligible in solid state. In this work rates of polymerization for N-tert-butylacrylamide and (N-tert-butylacrylamide)₂–ZnCl₂ are compared under various experimental conditions and overall activation energies are calculated.     

Synthesis and properties of a new polydiacetylene: Poly[1,6-di(N-carbazolyl)-2,4-hexadiyne]

The solid-state synthesis and properties are reported for a new polydiacetylene: poly[1,6-di(N-carbazolyl)-2,4-hexadiyne]. The monomer crystals polymerize quantitatively with γ irradiation or thermal annealing. An Autocatalytic effect is observed in both γ-ray polymerization and thermal polymerization and is attributed to an increase in chain propagation length at about 5% conversion. The activation energy for thermal polymerization is about 25 kcal/mole, independent of the degree of conversion to polymer. The exceptional thermal stability of the polymer crystals allowed a thermomechanical analysis over a large temperature range, ?50 to 300°C. With increasing temperature, the polymer contracts in the chain direction linearly with temperature over the entire range, yielding a thermal expansion coefficient of (?2.32 ± 0.02) × 10^?5°C^?1. Photoconductivity action spectra are reported for the polymer crystals. The energies for the photoconductivity onset (ca. 2.3 eV) and for the lowest energy optical transition (1.89 eV) are the lowest reported for the polydiacetylenes. The photoconduction onset is blue-shifted with respect to optical absorption—a result which is consistent with the excitonic assignment for the lowest energy optical transition in the polydiacetylenes.     

Topotactic solid-state polymerization of 3-aminocrotonamide by radiation

Radiation-induced solid-state polymerization of 3-aminocrotonamide (3-amino-2-butenamide) was carried out at room temperature, in open air atmosphere and under vacuum condition. The polymer obtained was white powder, soluble in methanol, but insoluble in water. The nature of polymers were investigated by IR, UV, x-ray, DP-MS, and elemental analysis to elucidate the mechanism of the polymerization. The polymer was crystalline with melting point in the range of 245–255°C. The cell parameters and space group of monomer and polymers were determined from powder x-ray diffraction patterns. The similarity of crystal structures of monomer and polymer indicated a topotactic polymerization. It was shown by spectroscopic investigations and elemental analyses that the polymerization proceeds by condensation reaction with evolution of one mole ammonia per two combined moles of monomer through a free radical mechanism. © 1996 John Wiley & Sons, Inc.     

RADIATION INDUCED SOLID-STATE POLYMERIZATION OF ACETYLENEDICARBOXYLIC ACID

ABSTRACT

Radiation induced solid-state polymerization of acetylenedicarboxylic acid was carried out at room temperature in open atmosphere and under vacuum conditions. The gray colored powder polymer obtained was insoluble in most common solvents but only partially soluble in DMSO and THF. The limiting conversion to polymer was about 5%. The polymer was characterized by IR, UV, DP-MS, DSC, TGA, and XRD. The mechanism of polymerization was elucidated from the available data. Polymerization followed a free radical mechanism. However, before the addition of monomer molecules to the growing chain, at least one of the carboxylic groups of the monomer breaks away as CO or CO₂. The formation of side group cyclization takes place. At least one of the bonds in the side cyclic group is an etheric bond. The DSC, TGA, and XRD results showed that the polymer was partially crystalline and showed no melting up to 1200°C. The mechanism of polymerization and assigned chain structure was studied by the direct pyrolysis mass spectrometric method.

The crystal structure of monomer and polymer was investigated by the XRD method. Both monomer and crystalline polymer were monoclinic with similar cell parameters. Thus, the polymerization follows a topotactic mechanism. The unpolymerized monomer retains its crystal structure and, therefore, CO or CO₂ in the monomer molecule has to be eliminated before polymerization could take place.     

Solid-state polymerization of hexaphenylcyclotrisiloxane

The anionic solid-state polymerization of triclinic crystals of hexaphenylcyclotrisiloxane (HPhTS) initiated by KOH and potassium oligo(methylphenylsiloxane) has been studied. It was found that this reaction can yield high molecular weight poly(diphenylsiloxane) (PDPhS) with a specific viscosity up to 5 (1 wt % diphenyloxide solution at 145°C). The main features of the process are as follows: (a) this is a heterogeneous reaction that proceeds inward from the surface of HPhTS crystals; (b) the crystalline polymer is obtained from the crystalline trimer; (c) OPhTS simultaneously forms along with the polymer; (d) the specific viscosity of the resulting polymer remains constant or decreases with polymerization time and, consequently, with the conversion of HPhTS; and (e) the crystallinity of polymerized PDPhS samples depends inversely on its specific viscosity. Together, these features suggest that polymerization and crystallization proceed successively. The morphologies of the resulting PDPhS phase revealed by means of scanning electron microscopy are consistent with this mechanism. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1973–1984, 1997     

Dispersion copolymerization of poly(oxyethylene) macromonomers and styrene

The kinetics of dispersion copolymerization of methacryloyl-terminated poly(oxyethylene) (PEO-MA) and p-vinylbenzyl-terminated (PEO-St) polyoxyethylene macromonomers and styrene (St), initiated by a water- and/or oil-soluble initiator, was investigated using conventional gravimetric and NMR methods at 60°C. The batch copolymerizations in the water/ethanol continuous phase were conducted to high conversion. The rate of polymerization was described by the curve with a maximum at very low conversion. The initial rate of polymerization and the number-average molecular weight were found to decrease with increasing [PEO-MA], and the decrease was more pronounced in the range of a high macromonomer concentration. The rate per particle (at ca. 20% conversion) was found to be proportional to the −1.55th, the particle size to the −0.92nd, and the number of particles (at final conversion) to the 3.2nd power of [PEO-MA], respectively. At the beginning of polymerization the continuous phase is the main reaction locus. As the polymerization advances, the reaction locus is shifted from the continuous phase to the polymer particles. The transform of the reaction loci from the continuous phase to the polymer particles increases the rate of polymerization and the polymer molecular weights. The increase of the weight ratio PEO-MA/St favors the formation of monodisperse polymer particles, the colloidal stability of dispersion, and the formation of a larger number of polymer particles. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3131–3139, 1997     

Polymerization of vinyl chloride in the presence of precipitants. I

The kinetics of bulk and precipitation polymerization of vinyl chloride has been studied over wide range of reaction temperature by using γ-ray induced initiation. The autoacceleration effect, which has been observed by many investigators in the case of chemically initiated bulk polymerization of vinyl chloride above 40°C and has been the most controversial aspect of the bulk polymerization of vinyl chloride, was found to disappear in the bulk polymerization below 0°C. In the bulk polymerization at 40°C, the autoacceleration effect was observed up to 20%, in agreement with the results of previous investigators, and a pronounced effect of the size of polymer particles on the time–conversion curve was observed. The kinetics of precipitation polymerization of vinyl chloride in the presence of some nonsolvents was successfully described by a oneparameter equation. A kinetic scheme, which clearly explains the zero-order reaction behavior of bulk polymerization at low temperature and the kinetic behavior of precipitation polymerization described by the empirical equation, is proposed. The autoacceleration effect in the bulk polymerization at 40°C was considered to be essentially the same phenomenon as the small retardation period observed in the bulk polymerization at low temperature.     

A novel organic intercalation system with layered polymer crystals as the host compounds derived from 1,3-diene carboxylic acids

A new type of organic intercalation system using poly(muconic acid) and poly(sorbic acid) crystals as the host compounds is described. The layered polymer crystals as the host are derived from benzyl-, dodecyl-, or naphthylmethylammonium salts of (Z,Z)-muconic or (E,E)-sorbic acids by topochemical polymerization. The subsequent solid-state hydrolysis of the resulting ammonium polymer crystals provides the corresponding carboxylic acid polymer crystals. When alkylamines are reacted with poly(muconic acid) or poly(sorbic acid) crystals dispersed in methanol at room temperature for a few hours, the intercalation proceeds to give layered ammonium polymer crystals via solid-state reactions, in which the polymers maintain a layered structure throughout. The interplanar spacing value of the polymer crystals changes according to the size of the guest molecules; that is, it exactly depends on the carbon number of the alkylamines used for each reaction of poly(muconic acid) or poly(sorbic acid) crystals. The stacking structure of alkyl chains with a tilt in the intercalated alkylammonium layers exists irrespective of the chemical and crystal structures of the host polymers. The intercalation of higher alkylamines into poly(muconic acid) crystals proceeds fast and quantitatively, while the conversion is dependent on the reaction conditions such as the structure and amount of the amine and the reaction time during the intercalation with poly(sorbic acid) crystals, due to the difference in the repeating layered structures of these polymer crystals. Some functional amines are also used as the guest molecules for this organic intercalation system.     

Dielectric properties of single crystals of the substituted diacetylene pTS: effect of the solid-state polymerization and phase transitions

Dielectric permittivities of the polymerizable organic solid, pTS diacetylene have been measured between 115 and 330 K in the directions parallel and perpendicular to the direction of polymer chain growth. The upper phase transition in monomer, polymer and mixed crystals at various stages of the solid-state polymerization manifests itself as a maximum in the temperature dependence of ε measured in the direction parallel to the molecular stacks, being particularly well pronounced in fully polymerized crystals. The transition was identified as an antiferroelectric one, the sublattice polarization being most probably the order parameter. The lower phase transition could be observed only in monomer and monomer-rich crystals as a shoulder on the ε(T) dependence. This transition could be detected only in the crystals containing less than ≈ 10–15% of polymer. The dielectric permittivity was found to be independent of frequency up to 3 GHz. The polymerization results in changes of the dielectric permittivity. In samples where the direction of measurements coincides with the b axis, these changes follow the monomer-polymer conversion curve.     

Radiation-induced solid-state polymerization of derivatives of methacrylic acid. II. Postirradiation polymerization of octadecyl methacrylate

Octadecyl methacrylate (mpc ≈ 12°C.) polymerized readily in the solid state in the temperature range ?30 to +12°C. after gamma irradiation at ?196°C. The initial rate of polymerization and the “limiting” conversion increased with radiation dose and temperature. The temperature dependence of the rate corresponded to an “apparent” activation energy of 20 kcal./mole. Difficulties were experienced with polymerization during separation of the polymer from residual monomer, but these were minimized by using low radiation doses and a hot, selective solvent. The maximum conversion achieved was 70%. The polymer was crosslinked, even at low conversions.     

High-pressure reactions. II. γ-Ray polymerization of acrylamide

The post-irradiation effect of high pressure on the γ-ray-initiated solid-state polymerization of acrylamide has been described. Polymer conversion was found to increase significantly with applied pressure. The molecular weight of polymer increases with pressure.     

Effects of water,methanol, and ethanol on the production of starch-g-polystyrene copolymers by cobalt-60 irradiation

Starch-g-polystyrene copolymers were made by simultaneous ⁶⁰Co irradiation of mixtures of wheat starch and styrene at room temperature. The extent of conversion of monomer to polymer is increased drastically with increasing water content up to a level of about 26 wt % on starch. Methanol had approximately the same effect as water at equivalent concentrations but ethanol was clearly less effective as a promoter of homo- and graft copolymerizations. Drying the starch reduced the conversion to polymer with all promoters but caused the greatest deterioration in the ability of ethanol to promote polymerization. The effects of physically swelling the starch by freeze drying the gelatinized material were also studied, as were preirradiation graft copolymerizations. The effects of promoters on graft polymerization parallel their abilities to scavenge stable radicals in irradiated starch. Water and methanol are better radical scavengers and polymerization promoters because they are better able to disrupt hydrogen bonds and permeate the starch structure. Radiolysis of the promoter is important in the grafting reaction.     

茂基二价钐配合物高效催化己内酯开环聚合

研究了二茂基二价钐配合物(C5H5)2Sm(THF)作为单组分催化剂催化己内脂开环聚合反应,考察了催化剂用量、聚合反应时间、聚合反应温度对己内酯聚合反应的影响。结果表明,配合物(C5H5)2Sm(THF)对己内酯聚合有极高的催化活性且产物的数均分子量较高,当催化剂与单体摩尔比为1：5000时,聚合产率仍可达50.3%,数均分子量可高达32.4万;温度升高,聚合反应的转化率增加,聚合产物数均分子量降低;催化剂用量增加,聚合转化率增加,聚合产物分子量降低;聚合产物的分子量分布较窄;通过凝胶色谱法对聚合产物的分子量及分子量分布进行了表征。     

Synthesis and characterization of high cis-polybutadiene: influence of monomer concentration and reaction temperature

This paper reports the study of the dependence of reaction conversion, catalyst activity, polymer microstructure, molecular weight, molecular weight distribution curves and Mooney viscosity on reaction temperature and monomer concentration in the reaction medium used in the synthesis of high cis-polybutadiene. A ternary catalyst system composed by neodymium versatate, trans-butyl chloride and diisobutylaluminum hydride was used in its synthesis. The highest molecular weights were obtained at polymerization temperatures in the range from 70 to 80 °C. The highest content of cis-1,4 repeating units (about 99%) was observed when the polymerization was carried out at the lowest initial monomer concentration (0.56 mol/l).