Anionic ring opening polymerization of 1-phenyl-1-vinyl-1-silacyclopent-3-ene

Summary Poly(1-phenyl-1-vinyl-1-sila-cis-pent-3-ene) (I) has been prepared by the anionic ring opening polymerization of 1-phenyl-1-vinyl-1-silacyclopent-3-ene (II) co-catalyzed by n-butyllithium and hexamethylphosphoramide (HMPA) in THF at-78°C. I has been characterized by ¹H, ¹³C and ²⁹Si NMR as well as by IR and UV spectroscopy. The molecular weight distribution of I has been determined by gel permeation chromatography (GPC), its thermal stability by thermogravimetric analysis (TGA) and its glass transition temperature (T_g) by differential scanning calorimetry (DSC). Thermal degradation of I in an inert atmosphere gives a twenty-seven percent char yield.     

Anionic ring opening polymerization of 3,4-benzo-1,1-dimethyl-1-silacyclopentene

Summary Treatment of 3,4-benzo-1,1-dimethyl-1-silacyclopentene with a catalytic amount of n-butyllithium and HMPA in THF yields poly(3,4-benzo-1,1-dimethyl-1-silapentene). This polymer has the highest melting temperature, glass transition temperature and thermal stability of any poly (1-silapent-3-ene) yet prepared.     

Ring opening metathesis polymerization of 1,1-diphenyl-1-sila-cyclopent-3-ene

Summary 1,1-Diphenyl-1-silacyclopent-3-ene (I) has been polymerized by ring opening metathesis using tungsten hexachloride and either cyclopentene or cyclohexene as an initiator, with or without tetraphenyltin as a cocatalyst. The product polymer poly(1,1-diphenyl-1-sila-cis-pent-3-ene) (II) has been characterized by¹H,¹³C, and²⁹Si NMR and IR spectroscopy.     

Metathesis ring opening polymerization of 5,6-dimethylenebicyclo[2.2.1]hept-2-ene

5,6-Dimethylenebicyclo[2.2.1]hept-2-ene ( I ) polymerizes in the presence of the two-component ring opening metathesis polymerization (ROMP) initiators WCl₆/(CH₃)4Sn and MoCl₅/(CH₃)4Sn. The product polymers were insoluble in all of many solvents investigated and are presumably cross-linked. The product polymers were investigated by IR and solid state ¹³C NMR spectroscopy, which established that the material consisted predominantly of poly(1,4-(2,3-dimethylene-cyclopentylene)vinylene) ( II ). A possible alternative route to II via thermal dehydrochlorination of poly(1,4-(2,3-bis(chloromethyl)cyclopentylene) vinylene) ( IV ) was also examined.     

Bulk anionic ring opening polymerization of silacyclopent-3-enes

Summary Poly[1,1-diphenyl-1-sila-cis-pent-3-ene](I), poly[1,1-dimethyl-1-sila-cis-pent-3-ene](II), poly[1-methyl-1-phenyl-1-sila-cis-pent-3-ene](III), poly[1-methyl-sila-cis-pent-3-ene](IV), and poly[1-phenyl-1-sila-cis-pent-3-ene](V) were prepared by bulk anionic ring opening polymerization of the corresponding 1-silacyclopent-3-enes, at room temperature by use n-butyllithium or t-butyllithium and HMPA as co-catalysts. No solvent (THF or diethyl ether) was utilized.     

Hydrogenation of ring opening metathesis polymerization polymers

Various methods of hydrogenating ring opening metathesis polymerization (ROMP) polymers were investigated as part of an effort to improve their stability and increase their usefulness as matrix materials for nanocluster synthesis. Hydrogenation with Pd/BaSO₄ catalyst in high-pressure hydrogen gas was only partly successful and limited to unfunctionalized polymers such as polymethyltetracyclododecene. Block copolymers containing phosphine or carboxylic acid functionalities were successfully hydrogenated by diimide generated in situ from p toluenesulfonylhydrazide. © 1995 John Wiley & Sons, Inc.     

Studies on the ring opening polymerization of caprolactone

The polymerization of -caprolactone(CL) with tetraphenylporphyrin(TPP)-diethylaluminium chloride(Et₂AlCl) or Et₂AlCl as initiator in toluene at 80° C gove a polymer with narrow molecular weight distribution.The effects of the temperature and the concentration of catalyst on the polymerization rate and the molecular weight of polymer were studied.     

开环聚合法制备聚D-乳酸的初步研究

以辛酸亚锡(SnOct2)为催化剂通过开环聚合反应由D-丙交酯(D-LA)制备聚D-乳酸(PDLA),并采用红外光谱(FTIR)、核磁共振(NMR)、差示扫描量热法(DSC)以及乌氏粘度计等对聚合产物进行表征。结果表明,聚合温度、聚合时间、催化剂用量以及真空度对PDLA的相对分子质量均有显著的影响,当聚合温度为160℃,聚合时间为20 h,催化剂用量为D-LA的0.03%以及真空度为60 Pa的条件下,可以得到粘均相对分子质量为26.5×104的PDLA产物。     

New aspects by ring opening polymerization of a spiro ketenacetal

Summary The ring opening polymerization of 3,9-bismethylene-2, 4, 8, 10-tetraoxa-spiro[5,5]undecane was investigated. It was shown that this bifunctional ketenacetal undergoes a radical homo- and copolymerization forming crosslinked polymers with a high degree of ring opened units. Using other initiators than radicals it is possible to get statements about the electronical state of ketenacetal functions in saturated heterocycles.     

Cationic ring opening polymerization of octamethylcyclotetrasiloxane initiated by solid superacid

Kinetics of the cationic ring opening polymerization of octamethylcyclotetrasiloxane (D₄) in bulk initiated by solid superacid was studied. The optimalizing experimental conditions were based on preliminary experiments. Higher temperature was beneficial to equilibrium conversion while stirring intensity beyond a certain level displayed no obvious effect on the rate of the reaction. A kinetic model was elicited and kinetic parameters were obtained through optimization. The calculated activation energies were 32.6 and 34.1 kJ mol^–1 for D4 and all other annuluses (D_x), respectively.     

酸白土催化体系开环八甲基环四硅氧烷的研究及机理探讨

Cationic ring opening polymerization of octamethylcyclotetrasiloxane （Da） initiated by acid treated bentonite was investigated. The experimental conditions were chosen on the basis of preliminary experiments.Higher temperature was found beneficial for the reaction process while stirring intensity beyond a certain level showed no obvious effect on the reaction rate. Polymers were characterized by Fourier transform infrared, proton nuclear magnetic resonance （IH-NMR） and gel perneation chromotography. The width of molecular mass distribution was found ranging between 1.2 and 1.4, which is extraordinarlly narrow compared with that of cationic polymerizations reported elsewhere （〉 1.9）. The results were believed due to the absence of free proton and counter ion which simplifies the polymerization process and the huge steric hindrance provided by bentonite particles which keeps the propagation of polysiloxane onto the surface of bentonite particles in a much more regular way. A feasible mechanism is proposed and seems to be supported well by experiments. Additionally, from the results of α, ω-dihydrogen terminated polysiloxanes prepared, the possibility of applying this potential environmentally friendly heterogeneous catalyst in industrial polymerization of cyclosiloxanes is anticipated.     

Towards a continuous process in heterogeneous coordinated anionic ring opening polymerization

Summary The current article deals with the initial developments of the use of a continuous plug flow reactor using an original heterogeneous catalyst system for the living coordinated anionic polymerization of certain oxygenated rings. This reactor is designed in order to maintain the essential characteristics of the original batch system. One of the pertinent parameters considered here is the residence time of the reactants inside the reactor. The column has been used to investigate ethylene oxide and -caprolactone oligomerization. Initial experiments have pointed out how the molecular weights can depend on the flow rate for a fixed bed length. Some theoretical problems relative to the reactive column are discussed in order to investigate more in depth the properties of this original continuous process and to model it to find the optimal working conditions.     

Anionic polymerization of acrylates

Summary The article presents preliminary results of the anionic polymerization of 2-ethylhexyl- and butyl acrylates initiated by ester enolate in the presence of Li 3-methylpentoxide-3. Compared with the Li t-butoxide which has been widely used earlier, this alkoxide is a more efficient stabilizer of active centers. Under selectively chosen reaction conditions, polymerizations of both monomers proceed quantitatively with a small extent of the selftermination event at-40 and-20°C producing polymers with narrow MWD's.     

Anionic polymerization of vinylsilanes

Summary The anionic polymerization of dimethylphenylvinylsilane with sec-butyllithium/N,N,N,N-tetramethylethylenediamine (TMEDA) was investigated. The polymerization proceeded up to 100% yield and afforded the polymer having isomerized-structure units. The polymerization was accompanied by chain transfer reaction to the monomer and the polymerization rate in the presence of TMEDA was much lower than in the absence of TMEDA.     

Polydispersity control in ring opening metathesis polymerization of amphiphilic norbornene diblock copolymers

Ring opening metathesis polymerization (ROMP) with Grubbs's catalyst was used to synthesize narrow polydispersity (PDI)diblock copolymers of norbornene (NOR) and norbornenedicarboxylic acid (NORCOOH). Norbornene (NOR) and 5-norbornene-2,3,-dicarboxylic acid bis trimethylsilyl ester (NORCOOTMS) were used as precursor monomers for thepolymerization. [NORCOOTMS]_m/[NOR]_n was converted to [NORCOOH]_m/[NOR]_n by precipitating the polymer solution in a mixture of methanol, acetic acid, and water. The conversion to 5-norbornene-2,3-dicarboxylic acid was evidenced by ¹H NMR. By polymerizing the bulkier NORCOOTMS precursor monomer first, lower PDIs were observed for the completed [NORCOOH]_m/[NOR]_n block copolymers in comparison to copolymers where the NOR block was polymerized first. The PDI of the diblock copolymers of [NORCOOH]_m/[NOR]_n decreased with increase in block length ofthe precursor NORCOOTMS monomer. This study shows that the PDI can be controlled by selecting a monomer with appropriate functionality as the starting block of the block copolymer to control the rate of propagation, R_p, as an alternative of using additives to change the reactivity of the catalyst.     

醇洗法纯化乙交酯的工艺及对开环聚合反应的影响

对本体解聚制备的乙交酯粗品进行醇洗纯化,研究了醇洗次数、溶剂用量、醇洗时间对乙交酯中游离酸、水含量及收率的影响;考察了醇洗后乙交酯中总氢质子含量对聚合反应的影响.筛选了不同醇类溶剂,优选异丙醇为合适的溶剂进行乙交酯粗品纯化,辅以抽滤、真空干燥等手段最终得到纯化的乙交酯.研究结果表明,醇洗次数3次,溶剂用量即V(醇)/M(乙交酯)=2mL/g,洗涤时间30min,乙交酯中的游离酸、水含量分别降低到1.7×10^-5mol/g、468mg/L,总氢质子含量为43×10^-6mol/g,通过双螺杆挤出机进行开环聚合,得到聚乙醇酸(PGA)特性黏度高达0.81dL/g;收率可达82%,比重结晶法纯化收率高.通过差示扫描量热法(DSC)测定醇洗后乙交酯纯度,得均值99.93%,满足聚合纯度的要求.     

Synthesizing and characterization of comb-shaped carbazole containing copolymer via combination of ring opening polymerization and nitroxide-mediated polymerization

The macro-TEMPO agent (poly(4-glycidyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl), PGTEMPO) was synthesized by anion ring-opening polymerization (ROP) of 4-glycidyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl (GTEMPO) using potassium t-butoxide as the initiator. The comb-shaped copolymer, PGTEMPO-g-PVBK, was prepared via nitroxide-mediated free radical polymerization (NMP) using PGTEMPO as macro-TEMPO agent and 9-(4-vinylbenzyl)-9H-carbazole (VBK) as the monomer. The polymerizations showed characteristics of “living”/controlled behavior. The optical properties, thermal analysis and electrochemical properties of the comb-shaped copolymers were investigated. The fluorescence and ultraviolet intensity and cyclic voltammetries of the comb-shaped copolymers with different molecular weight showed a regular order.     

Ring-opening polymerization of 1 -ethylbicyclo[2.2.1] hept-2-ene

1-Ethylbicyclo[2.2.1]hept-2-ene has been polymerized using a range of metathesis catalysts and the structure of the polymers determined by ¹³C n.m.r. spectroscopy. For a given catalyst the cis double bond content was lower and the head-tail bias greater than for polymers of the 1-methyl analogue. This is interpreted in terms of enhanced steric and polar effects brought about by the ethyl substituent.