Microwave-Irradiated Ring-Opening Polymerization of Octamethylcyclotetrasiloxane in the Presence of Water

α, ω-dihydroxyl polydimethylsiloxane (DHPDMS) was prepared via anionic ring-opening polymerization of octamethyl cyclotetrasiloxane (D₄) under microwave irradiation (MI) in the presence of water. The conversion and polymerization rate were calculated by the gravimetric method. The effect of microwave power on the polymerization was investigated. FTIR was used to verify the DHPDMS prepared at different irradiation times. The results show that the conversion is the highest when the initial microwave power is preset at 700 W. Compared with conventional heating (CH), the polymerization rate and equilibrium conversion are both enhanced by the introduction of microwave irradiation. The species and concentration of the cyclosiloxane mixture caused by backbiting reaction were determined by gas chromatography/mass spectrometry (GC/MS). The lower concentration of cyclosiloxane in the polymer prepared under MI indicates that side reactions have been reduced and a pure polymer obtained. The molecular weight and polydispersity index (PDI) measured by GPC show that under MI, the molecular weight of DHPDMS is lower and PDI is narrower than those under CH.     

原子转移自由基聚合法（ATRP）制备聚丙烯酰胺

以苄基氯为引发剂,氯化亚铁为催化剂,三苯基膦为配体研究了丙烯酰胺在N,N-二甲基甲酰胺中的原子转移自由基聚合,考察了聚合时间、催化剂与配体的摩尔配比、温度等因素对单体转化率、分子量的影响。结果表明：80℃下,[AM]/[C6H5CH2Cl]/[FeCl2]/[PPh3]=100/1/0.5/1时,聚丙烯酰胺分子量随单体转化率增加线性增大,ln[[MM]]0与聚合时间呈线性关系,温度对聚合特征有较大影响。     

Emulsion polymerization of styrene under pulsed microwave irradiation

We performed the emulsion polymerization of styrene successfully with potassium persulfate (KPS) as an initiator and sodium dodecylsulfonate as an emulsifier under high‐power pulsed microwave irradiation (PMI). We investigated the effects of the temperature, the concentration of initiator, and various parameters of PMI (i.e., irradiation power, duty cycle, irradiation energy, and pulse width) on the polymerization. The results indicated that PMI, compared to conventional heating (CH), caused a significant increase in the decomposition rate of KPS (2.4 times higher than that under CH at about 70°C) and in the amount of particles (5 times higher than that under CH); consequently, the polymerization rate was effectively enhanced. For initiator concentrations of 0.10 and 0.20 wt %, the enhancement of the polymerization rate under PMI was 129 and 38% greater, respectively, than that under CH. The glass‐transition temperature and the regularity composition of the polymers under PMI and CH showed no difference, which indicated that PMI had little effect on the physical properties and microstructure of the polymer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 28–35, 2003     

Atom transfer radical suspension polymerization of methyl methacrylate catalyzed by CuCl/bpy

Atom transfer radical suspension polymerization (suspension ATRP) of methyl methacrylate (MMA) was carried out using 1-chloro-1-phenylethane (1-PECl) as initiator, copper chloride/bipyridine (CuCl/bpy) as catalyst. The polymerization was accomplished with a mechanical agitator under the protection of nitrogen atmosphere. Apart from the dispersing agent (1% PVA), NaCl was also used in the water phase to decrease the diffusion of CuCl/bpy to water and the influence of the concentration of NaCl was investigated. Subsequently, the kinetic behavior of the suspension ATRP of MMA at different temperatures was studied. At 90 and 95 °C, the polymerization showed first order with respect to monomer concentration until high conversion. The molecular weight (M_n) of the polymer increased with monomer conversion. However, at lower temperatures, different levels of autoacceleration was observed. The polymerization deviated from first order with respect to monomer concentration when the conversion was up to some degree. The lower the temperature was, the more the deviation displayed. On comparison with bulk ATRP of MMA, the rate of suspension ATRP was much faster.     

Controlled/‘living’ radical polymerization of methyl methacrylate with p-TsCl/CuBr/BPY initiating system under microwave irradiation

Atom-transfer radical polymerization of methyl methacrylate under microwave irradiation (MI) using p-TsCl/CuBr/BPY as the initiating system was successfully carried out. The polymerization of methyl methacrylate under MI shows linear first-order rate plots, a linear increase in the number-average molecular weight with conversion and low polydispersities, 1.1 < M_w/M_n < 1.3. The influence of polymerization time, temperature and monomer/initiator ratio on the conversion, molecular weight and polymer distribution were studied using the MI process, and compared with that obtained by the corresponding conventional heating (CH) process. The MI process not only increases the rate of polymerization, but also narrows the polydispersity index of polymers. The apparent rate constant, , under MI is 6–8 times higher than that under CH with an identical initiating system and polymerization temperature. The effect of MI on the stereoregularity and T_g of PMMA were investigated by ¹³C NMR spectroscopy and DSC, respectively. Copyright © 2004 Society of Chemical Industry     

Synthesis and characterization of A-B-A triblock copolymers derived from chloro-telechelic poly(l-lactide): combining ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP)

Ring-opening polymerization (ROP) of l-lactide was combined with atom transfer radical polymerization (ATRP) to produce well-defined linear block copolymers. Poly(l-lactide) (PLLA) was synthesized via ROP using ethylene glycol as an initiator and stannous octoate as a catalyst. The isolated hydroxy-telechelic PLLA was reacted with thionyl chloride and pyridine in toluene to afford chloro-telechelic PLLA (Cl-PLLA-Cl). The latter was employed as a macroinitiator in the synthesis of A-B-A triblock copolymers having either tert-butyl acrylate or benzyl acrylate outer blocks. Outer-block molecular weight was targeted by the mole ratio of monomer (acrylate) to the PLLA chloride initiating sites. The actual incorporation of acrylate into the triblock copolymer was lower than the molar feed ratio as the copolymer became increasingly less soluble upon conversion of acrylate in all cases.     

ATRP of acrylonitrile catalyzed by FeCl2/succinic acid under microwave irradiation

A single‐pot atom‐transfer radical polymerization (ATRP) under microwave irradiation was first used to successfully synthesize polyacrylonitrile. This was achieved by using FeCl₂/succinic acid as the catalyst and 2‐chloropropionitrile as the initiator. Using the same experimental conditions, the apparent rate constant under microwave irradiation was found to be higher than that under conventional heating. The FeCl₂/succinic acid ratio of 1 : 2 not only gives the best control of molecular weight and its distribution but also provides rather rapid reaction rate. When FeCl₂ was replaced with CuCl, ATRP of AN does not show an obvious living characteristics. To demonstrate the active nature of the polymer chain end, the polymers were used as macroinitiators to proceed the chain‐extension polymerization. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1598–1601, 2006     

Microwave-assisted controlled copolymerization of styrene and acrylonitrile catalyzed by FeCl<Subscript>3</Subscript>/isophthalic acid

The copolymer of styrene-co-acrylonitrile (SAN) was synthesized by the atom transfer radical polymerization (ATRP) using FeCl₃-isophthalic acid (IA)/2,2′-azobis(isobutyronitrile) catalyst system under microwave irradiation (MI). Compared with conventional heating (CH), the copolymerization rate was accelerated under MI, and the conversion of monomer rapidly achieved 30% in 38 min for MI relative to 8% for CH under other same conditions. The kinetics results indicated that RATRP of St/AN is a ‘living’/controlled polymerization, corresponding to a linear increase of molecular weights with the increasing of monomer conversion and a relatively narrow polydispersities index (PDI < 1.25) when the conversion is beyond 30%. The resultant SAN was characterized by FT–IR, NMR, and GPC.     

PhCH2Cl/MoCl3(OC8H17)2/PPh3体系引发异戊二烯的原子转移自由基聚合

研究了以PhCH2Cl/MoCl3(OC8H17)2/PPh3体系引发异戊二烯的原子转移自由基聚合,所得聚合物的相对分子质量与转化率呈线性增加,相对分子质量分布为1.9 ~2.2。紫外光谱分析表明,该聚合反应符合原子转移自由基聚合机理。     

ARGET ATRP法合成聚氯乙烯接枝丙烯酸丁酯共聚物

以不稳定氯含量高的聚氯乙烯（U-PVC）和氯乙烯-溴代异丁酸烯丙酯共聚物（PVC-co-ABrMP）为大分子引发剂,使用电子转移催化再生原子转移自由基聚合（ARGET ATRP）进行丙烯酸丁酯（BA）的溶液接枝共聚。在固定CuCl₂：三（2-吡啶甲基）胺：辛酸亚锡（摩尔比）时,当CuCl₂用量（相对于氯乙烯链节数）小于0.1%时,BA转化率随CuCl₂用量增加而明显增加;辛酸亚锡与CuCl₂摩尔比大于50时,辛酸亚锡用量对聚合速率的影响较小;相同催化体系用量下,采用PVC-co-ABrMP为引发剂,可获得更高的BA转化率。通过PVC-co-ABrMP酯基水解得到PBA支链,其分子量分布指数为1.29,符合“活性”自由基聚合的特征。接枝PBA对PVC有明显的内增塑效果,PBA摩尔分数为32.75%的PVC-g-BA的玻璃化温度为8.34℃。     

Free‐radical bulk polymerization of styrene with a new trifunctional cyclic peroxide initiator

The bulk free‐radical polymerization of styrene in the presence of a new cyclic trifunctional initiator, 3,6,9‐triethyl‐3,6,9‐trimethyl‐1,4,7‐triperoxonane, was studied. Full‐conversion‐range experiments were carried out to assess the effects of the temperature and initiator concentration on the polymerization kinetics, molecular weight, and polydispersity. Gel permeation chromatography was used to measure the molecular weight and the molecular weight distribution of polystyrene. When this multifunctional initiator was used for styrene polymerization at higher temperatures, it was possible to produce polymers with higher molecular weights and narrower molecular weight polydispersity at a higher rate. This showed that the molecular weight and polydispersity were influenced by the initiator concentration and the polymerization temperature in an unusual manner. Moreover, polystyrene, obtained with trifunctional peroxide, had O? O bonds in the molecular chains and was investigated with differential scanning calorimetry and gel permeation chromatography. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1035–1042, 2004     

Atom transfer radical polymerization of lauryl methacrylate

The atom transfer radical polymerization (ATRP) of lauryl methacrylate (LMA) with an ethyl 2‐bromobutyrate/CuCl/N,N,N′,N″,N″‐pentamethyldiethylenetriamine initiation system was successfully carried out in toluene, and poly(lauryl methacrylate) with a low polydispersity (1.2 < weight‐average molecular weight/number‐average molecular weight < 1.5) was obtained. Plots of ln ([M])₀/([M]) versus time and plots of the molecular weight versus conversion showed a linear dependence, indicating a constant number of propagating species throughout the polymerization. The rate of polymerization was 0.56‐order with respect to the concentration of the initiator and 1.30‐order with respect to the concentration of the Cu(I) catalyst. In addition, the effect of the solvent on the polymerization was investigated, and the thermodynamic data and activation parameters for the solution ATRP of LMA were reported. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1117–1125, 2003     

Surface-initiated atom transfer radical polymerization of methyl methacrylate on magnetite nanoparticles

The synthesis of magnetite nanoparticles coated with a well-defined graft polymer is reported. The magnetite nanoparticles with an initiator group for copper-mediated atom transfer radical polymerization (ATRP), 2-(4-chlorosulfonylphenyl) ethyltrichlorosilane (CTCS) chemically bound on their surfaces were prepared by the self-assembled monolayer-deposition method. The surface-initiated ATRP of methyl methacrylate (MMA) was carried out with the CTCS-coated magnetite nanoparticles in the presence of free (sacrificing) initiator, p-toluenesulfonyl chloride. Polymerization proceeded in a living fashion, exhibiting first-order kinetics of monomer consumption and a proportional relationship between molecular weight of the graft polymer and monomer conversion, thus providing well-defined, low-polydispersity graft polymers with an approximate graft density of 0.7 chains/nm². The molecular weight and polydispersity of the graft polymer were nearly equal to those of the free polymer produced in the solution, meaning that the free polymer is a good measure of the characteristics of the graft polymer. The graft polymer possessed exceptionally high stability and remarkably improved dispersibility of the magnetite nanoparticles in organic solvent.     

The Effect of Initiators and Reaction Conditions on the Polymer Syntheses by Atom Transfer Radical Polymerization

The controlled/“living” radical polymerization of methyl methacrylate (MMA), 2-hydroxyethyl methacrylate (HEMA), and styrene by atom transfer radical polymerization (ATRP) is reported. The effect of initiators and reaction conditions on the ATRP results was investigated. Controlled polymerizations with predictable molecular weights were performed on MMA at 40^○C and 80^○C using a CuCl/bipyridine (bipy) catalyst system in conjunction with 1-bromoethyl benzene as the initiator. The addition of a polar solvent was necessary to decrease the polymerization rate and afford low polydispersity materials. The ATRP processes followed a first-order kinetics with respect to the monomer concentration. The molecular weights of the resulting polymers were very close to their calculated values and increased with the conversion. The ATRP results of styrene showed a similar trend and revealed that CuBr/bipy or CuBr/PMDETA was a more suitable catalyst system than CuCl/bipy. In addition, it was found that controlled polymerizations could be readily carried out both in a nonpolar solvent or in bulk. Furthermore, by using the bromine-terminated polymer as the macroinitiator, diblock copolymers of PSt-b-PMMA, PSt-b-PHEMA, PMMA-b-PSt, and PMMA-b-PHEMA could be obtained. Thermal analysis and X-ray diffraction studies confirmed the amorphous structures of the resulting polymers.     

High-pressure atom transfer radical polymerization of methyl methacrylate for well-defined ultrahigh molecular-weight polymers

The feasibility of high-pressure atom transfer radical polymerization (ATRP) for synthesizing well-defined polymers of extraordinarily high molecular weights was demonstrated. ATRP of methyl methacrylate (MMA) under pressures up to 500 MPa was investigated at 60 °C. The addition of a small amount of a Cu(II)Cl₂/ligand complex along with the general benefits of high pressure of enhancing propagation and suppressing termination brought about an excellent control of polymerization even with an extremely low concentration of ATRP initiator. For example, there was produced PMMA with a number-average molecular weight M_n of 3.6 × 10⁶ and a polydispersity index of 1.24, which had never been achieved by conventional ATRP.     

双硫酯作为链转移剂的苯乙烯本体聚合研究

研究了二硫代苯甲酸苄基酯（BDB）、二硫代苯甲酸苯乙基酯（PEDB）及二硫代苯甲酸异丙苯基酯（CDB）三种RAFT试剂作为链转移剂的苯乙烯本体聚合。动力学研究表明,当BDB及PEDB浓度和偶氮二异丁腈（AIBN）浓度同时增大时,AIBN浓度提高所导致的聚合反应速率提高起主导作用：当CDB和AIBN浓度同时提高时,CDB浓度提高所导致的聚合速率降低作用影响更显著。对CDB体系,随转化率提高分子量分布变宽。对BDB体系,当其浓度较高时,随转化率提高分子量分布变窄;当其浓度较低时,不利于实现可控,活性聚合,反应后期分子量分布变宽。动力学和GPC分析均表明以BDB为链转移剂时苯乙烯本体聚合的可控性最好。在同时考虑链转移剂和引发剂作用的基础上,提出了修正的聚合物分子量预测模型,该模型可有效预测以双硫酯为链转移剂的苯乙烯RAFT聚合体系的分子量。     

Poly(tert-butyl acrylate-b-isobutylene-b-styrene) terpolymer from a carbocationic initiator containing a latent radical initiating site

A poly(isobutylene-b-styrene) (PIB-PS) copolymer was synthesized via quasi-living carbocationic polymerization from an initiator containing a latent site for atom transfer radical polymerization (ATRP) initiation. The initiator, 3,3,5-trimethyl-5-chlorohexyl acetate (TMCHA), was synthesized in four steps from methyl 3,3-dimethyl-4-pentenoate. The PIB block was created at −70 °C in a methylcyclohexane/methyl chloride (60:40) cosolvent system, using TiCl₄ as the catalyst, followed by sequential addition of styrene. The acetate head group of the resulting block copolymer was converted to a hydroxyl group using a strong base and subsequently esterified with 2-bromopropionyl bromide to create an initiating site for ATRP of tert-butyl acrylate, which was carried out using a Cu(I)Br/1,1,4,7,7,-pentamethyl-diethylenetriamine (PMDETA) catalyst system. The final terpolymers had compositions that were very close to theoretical.     

ICAR ATRP of methyl methacrylate catalyzed by FeCl3·6H2O/succinic acid

In this work, methyl methacrylate (MMA) was polymerized by initiator for continuous activator regeneration (ICAR) atom transfer radical polymerization (ATRP) method to obtain low molecular weight living polymers. The ATRP initiator was ethyl 2‐bromoisobutyrate, the catalyst ligand complex system was FeCl₃·6H₂O/succinic acid, and the conventional radical initiator 2,2′‐azobisisobutyronitrile was used as a thermal radical initiator. Polymers with controlled molecular weight were obtained with ppm level of Fe catalyst complex at 90°C in N,N‐dimethylformamide. The polymer was characterized by nuclear magnetic resonance (NMR). The molecular weight and molecular weight distribution of the obtained poly (methyl methacrylate) were measured by gel permeation chromatography method. The kinetics results indicated that ICAR ATRP of MMA was a “living”/controlled polymerization, corresponding to a linear increase of molecular weights with the increasing of monomer conversion and a relatively narrow polydispersities index. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis of polyacrylonitrile via reverse ATRP initiated by 1,1,2,2‐tetraphenyl‐1,2‐ethanediol/CuCl2/2,2′‐bipyridine

The reverse atom‐transfer radical polymerization (RATRP) technique using CuCl₂/2,2′‐bipyridine (bipy) complex as a catalyst was applied to the living‐radical polymerization of acrylonitrile (AN). 1,1,2,2‐Tetraphenyl‐1,2‐ethanediol (TPED) was first used as the initiator in this copper‐based RATRP initiation system. A CuCl₂ to bipy ratio of 0.5 not only gives the best control of molecular weight and its distribution, but also provides rather rapid reaction rate. The rate of polymerization increases with increasing the polymerization temperature, and the apparent activation energy was calculated to be 53.2 kJ mol^?1. Because the polymers obtained were end‐functionalized by chlorine atoms, they were used as macroinitiators to proceed the chain extension polymerization in the presence of CuCl/bipy catalyst system via a conventional ATRP process. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3529–3533, 2007     

RATRP of MMA in AIBN/FeC1<Subscript>3</Subscript>/PPh<Subscript>3</Subscript> initiation system under microwave irradiation

Summary Reverse atom transfer radical polymerization (RATRP) of methyl methacrylate (MMA) under microwave irradiation (MI), using azobisisobutyronitrile (AIBN) /FeC1₃/triphenylphosphine (PPh₃) as the initiating system, was successfully carried out in N, N-dimethylformamide (DMF) at 69°C. Plots of In ([MI₀/[M]) vs. time and molecular weight evolution vs. conversion showed a linear dependence. A polymer for reaching 82% conversion, with molecular weight (M_n) 34,000 and polydispersity index (PDI) 1.37, was obtained under MI (90U') with the ratio of [MMA]₀/[AIBN]₀/[FeCl₃]₀/[PPh₃]₀ = 1600/2/4/8 in only 60 min; while 840 min was required under conventional heating (CH) process for reaching 82 % conversion (M_n = 48,000 and PDI = 1.31) at identical polymerization conditions, indicating a significant enhancement of the polymerization rates and apparent initiator efficiencies under MI. Received: 2 September 2002/Revised version: 3 October 2002/Accepted: 10 December 2002 Correspondence to Xiulin Zhu