甲基丙烯酸正丁酯正相微乳液可控/“活性”光聚合动力学研究

以末端含溴原子的光引发剂2-溴异丁酰氧基-2-甲基-1-苯基甲酮(HMPP-Br)为引发剂,2,2,6,6-四甲基哌啶-1-氧自由基(TEMPO)和2,2,6,6-四甲基哌啶醇(TMP)为调控剂,采用光聚合方法研究了甲基丙烯酸正丁酯(n-BMA)/十二烷基硫酸钠(SDS)/水/正丁醇 O/W型正相微乳液体系的光聚合反应动力学.结果表明,改性后的引发剂具有一定的引发活性,且聚合微乳液体系较稳定,聚合反应获得了良好的ln[M]₀/[M]与时间、数均分子量与转化率之间的线性动力学关系,制备了分子量分布较窄的Poly(n-BMA)均聚物.     

HTEMPO和TMPD调控下MMA可控/活性光聚合研究

以HTEMPO(2,2,6,6-四甲基-4-羟基哌啶-1-氧自由基)和TMPD(2,2,6,6-四甲基哌啶酮)为调控介质, 以Irgacure 651为引发剂, 研究了甲基丙烯酸甲酯(MMA)光聚合体系的控制反应动力学, 比较了单分子(HTEMPO为调控介质)和双分子(HTEMPO和TMPD为调控介质)调控体系, 并讨论了HTEMPO和HTEMPO/TMPD在MMA光聚合体系中的调控作用、 光敏化作用和原位光氧化反应. 结果表明, 对MMA光聚合体系, 以HTEMPO/TMPD为控制介质的双分子调控体系是有效的, 获得了良好的ln(\[M0\]/\[M\])与时间, 数均分子量与转化率之间的线性动力学关系, 并且PMMA均聚物的多分散性指数(PDI)随着转化率的提高而减小. 在高转化率(>85%)下, 体系的多分散性指数(PDI)最小值可达到1.2.     

负载型原子转移自由基聚合配体的合成及应用

用丙烯酸甲酯(MA)与负载到纳米二氧化硅有机/无机杂化粒子上的三乙烯四胺(TETA)进行Michael加成反应,合成了负载型原子转移自由基聚合(ATRP)配体。将其用于甲基丙烯酸甲酯(MMA)的ATRP,结果表明,动力学曲线表现为ln[c(M0)/c(Mt)](c(M0)为单体起始浓度,c(Mt)为反应时间t时单体浓度)与时间线性相关,分子量随转化率线性增加。可以通过离心轻易将催化体系从聚合物中分离出来,回收的催化体系可再次用于MMA的ATRP,且聚合反应仍具有可控/活性的特性,克服了传统ATRP中聚合后去除含过渡金属催化体系的困难。     

活性正离子聚合与原子转移自由基聚合转换合成聚β-蒎烯接枝共聚物

通过活性正离子聚合与原子转移自由基聚合(ATRP)转换合成了β-蒎烯与甲基丙烯酸甲酯(MMA)、丙烯酸丁酯(BA)、苯乙烯(St)的新型接枝共聚物.首先以α-氯代乙苯/TiCl4/Ti(OiPr)4/nBu4NCl体系引发β-蒎烯活性正离子聚合,合成预定分子量大小和窄分子量分布的聚β-蒎烯,然后经N-溴代琥珀酰亚胺(NBS)定量溴化,得到溴化聚β-蒎烯大分子引发剂(Br/β-蒎烯链节摩尔比为0.5).然后将该大分子引发剂与溴化亚铜(CuBr)/2,2′-联吡啶(bpy)复合,引发MMA、BA、St进行ATRP接枝聚合.接枝反应显示一级动力学特征,且产物的分子量及分子量分布可控,表明上述ATRP接枝聚合反应具有可控聚合特征.接枝产物的结构经1H-NMR分析得到进一步证实.     

ACPMA/BPO引发甲基丙烯酸甲酯聚合及其动力学

以4,4′-偶氮二[4-氰基戊酰(对-二甲氨基)苯胺](ACPMA)/过氧化二苯甲酰(BPO)为氧化还原引发体系,研究了甲基丙烯酸甲酯(MMA)在N,N-二甲基甲酰胺(DMF)中的聚合及其动力学行为.考察了聚合反应温度、单体浓度、ACPMA浓度和BPO浓度对聚合反应速率和聚合物分子量的影响,测定了反应级数和聚合反应的活化能.结果表明,在一定范围内,聚合反应速率随单体浓度增大、ACPMA浓度增大、BPO浓度增大和反应温度的升高而增大;聚合物分子量随单体浓度的增大而增大,随ACPMA浓度的增大、BPO浓度增大和反应温度的升高而降低.该体系具有氧化还原引发体系的特征,其引发MMA的聚合速率方程为Rp=K[ACPMA]0.57     

PADC-Cu(Ⅱ)/Na2SO3/H2O体系引发MMA聚合

由含N,O,S多官能团的螯合树脂PADC和Cu2 作用制得一种新型的高分子金属配合物,用IR、XPS、AAS、TG/DTA对其结构进行了表征.以该配合物和Na2SO3水溶液组成的体系应用于引发MMA聚合,结果表明:PADC-Cu(Ⅱ)/Na2SO3体系可以有效地引发MMA聚合,反应表观活化能Ea=57.4 kJmol-1,并详细研究了影响产率和分子量的各因素,由该体系引发MMA聚合的分子量可达213万,在6h内产率就达58.6%.初步讨论了该聚合过程是一种自由基聚合过程,初始自由基由PADC-Cu2 /Na2SO3/MMA体系“配位氢转移”产生.     

乳液体系中的RAFT可控/活性自由基聚合研究进展

可逆加成-断裂链转移聚合(RAFT)是新近发展起来的可控/活性自由基聚合方法。由于该方法具有适用单体范围广、反应条件温和、可采用多种聚合实施方法等优点,已成为一种有效的分子设计手段。本文总结了近几年文献报道的在乳液和细乳液体系中实施RAFT聚合反应的研究进展,对非均相体系的稳定性、聚合反应过程中的动力学特点、以及聚合产物的分子量及其分布等方面的研究进行了综述。     

P(MMA-M12-BPMA)乳液的合成及紫外吸收性能

以甲基丙烯酸甲酯(MMA)、可聚合乳化剂马来酸酐衍生物磺酸钠(M12)和可聚合紫外线吸收剂2-羟基-4-(3-甲基丙烯酰氧基-2-羟基丙氧基)苯甲酮(BPMA)为原料,采用乳液聚合方法制备了P(MMA-M12-BP-MA)共聚物乳液。通过转化率、红外光谱、以及紫外吸收光谱测定,分别研究了M12含量对聚合反应速率的影响、所得共聚产物的结构、以及共聚物乳液和共聚物紫外吸收特性。结果表明,随M12含量增大,聚合反应速率增加;BPMA含量增大有利于提高共聚物乳液和共聚物紫外吸收性能。     

RAFT聚合合成一种即含甲酰基又含手性β-蒎烯单元聚合物

设计并合成了一种新型含甲酰基同时又含β-蒎烯单元的新单体2-β-蒎氧基-5-乙烯基苯甲醛(POVB),选择苯基双硫代乙酸1-苯基乙酯(PEPDA)为RAFT试剂、以AIBN为引发剂、在60℃下THF中实现了POVB的"活性"/可控RAFT自由基聚合.单体浓度半对数ln([M]0/[M])与聚合时间符合线性关系,聚合过程呈现一级动力学特征;聚合物分子量(Mn)随单体转化率几乎线性增加,而且整个反应过程中分子量分布(Mw/Mn1.2)保持在较窄的范围.1H-NMR的分析进一步证实了聚合物链的末端精细结构.此外,CD谱结果表明手性单元β-蒎烯基能赋予聚合物以光学活性.     

乙烯系自由基聚合阻聚效应(XⅧ)──哌啶氮氧自由基氨基硫脲化合物与通用阻聚剂混合对MMA阻聚效应研究

本文研究了3种1-(芳酰基)-4[4'-(2,2,6,6-四甲基哌啶)-1-氧自由基]氨基硫脲化合物(ATSCPO)分别同通用阻聚剂(CIH),如对苯二酚(HQ)、苯醌(BQ)、吩噻嗪(PT)及二乙羟胺(DEHA)组成的混合阻聚剂对AIBN引发的MMA自由基聚合的影响。研究结果表明:当[ATSCPO]/CIH=5:1时,除ATSCPO-BQ外,其余阻聚效果均较ATSCPO和CIH单独用作阻聚剂时高,如聚合反应诱导期延长、聚合速率下降、聚合物粘均分子量变小等,表明ATSCPO和CHI间有协同效应。通过对阻聚因素的考察,得出阻聚剂的活性次序为ATSCPOHQ>ATSCPO-PT>ATSCPO-DEHA≈ATSCPO-BQ.     

Controlled/living photopolymerization of methyl methacrylate in miniemulsion mediated by HTEMPO

Controlled/living photopolymerization of methyl methacrylate (MMA) in miniemulsion mediated by 4-hydroxy-2,2,6,6-tetramethyl-piperidinyloxy (HTEMPO) was carried out at ambient temperatures. MMA miniemulsion was prepared by using an anionic surfactant with cetylalcohol as a co-stabilizer. The photopolymerization led to stable lattices and they were obtained with no coagulation during synthesis and no destabilization over time. It was found that the obtained MMA homopolymers exhibited relatively narrow molecular weight distribution (PDI = 1.27 − 1.36) which was characterized by GPC. The plots of number-average molecular weight in (M _n) vs. conversion and ln([M₀]/[M]) vs. time both were linear indicating that the reaction was a controlled/living free radical polymerization. __________ Translated from Chemical Journal of Chinese Universities, 2007, 28(4): 774–778 [译自: 高等学校化学学报]     

Butyl acrylate/methyl methacrylate latexes: adhesive properties

In this study, butyl acrylate/methyl methacrylate (BA/MMA) latexes of bimodal molecular weight and particle size distribution were prepared in a multi-step process by seeded conventional emulsion and seeded miniemulsion polymerization. For the conventional emulsion case, a BA/MMA batch copolymerization was conducted as a first step (seed generation) and was followed by a monomer addition step to ensure particle growth. In a third step, a BA/MMA pre-emulsified mixture was added to generate a second particle population. For the miniemulsion case, a BA/MMA copolymerization was carried out as a first step (seed generation) and was followed by a monomer addition step. The addition of a BA/MMA miniemulsion served to generate a bimodal particle size and molecular weight distribution. The final latexes were coated onto a polyethylene terephthalate carrier, dried and their performance as pressure-sensitive adhesives was evaluated using tack, peel and shear adhesion measurements. Structure-property relationships between the adhesive properties and the weight-average molecular weight and average particle size were examined. Even though the polymers obtained by miniemulsion showed better shear resistance, their shear resistance was low. There was no statistically significant difference in peel resistance of the polymers obtained by the two reactions. While a significant difference in tackiness between the two emulsion procedures was found when the adhesives were tested using the less sensitive, rolling ball test, no differences were found when they were tested using a loop tack test.     

Controlled Radical Photopolymerization of n-Butyl Methacrylate in Bluk Mediated by HTEMPO

Recently, controlled free-radical polymerization (CRP) has been a technique for the preparation of polymers of tailored architectures using experimentally simple techniques1. The CRP methods were nitroxide-mediated free radical polymerization (NMP), atom …     

β-CD存在下MMA细乳液体系的RAFT聚合

近年来，活性自由基聚合已成为高分子合成领域中的一个热门课题．Rizzardo研究小组提出了一种新型活性自由基聚合反应，即RAFT(Reversible addition-fragmentation chain transfer)聚合．RAFT反应在传统的自由基聚合中加入了具有高链转移常数和特定结构的链转移剂——双硫酯类化合物．当链转移剂的浓度足够大时，链转移反应由不可逆变为可逆，聚合反应也随之发生质的变化，由不可控     

Radical polymerization of methyl methacrylate with ethane-1,1,2-triyltribenzene as an initiator and ethane-1,1,2-triyltribenzene-end polymers as macroinitiators

An unsymmetrical triphenylethane, ethane-1,1,2-triyltribenzene (ETB), was successfully prepared from phenyl lithium, trans-1,2-diphenylethylene, and methanol. Characterization of the compound was performed by ¹H and ¹³C nuclear magnetic resonance spectroscopy (NMR). The polymerization of methyl methacrylate (MMA) was performed in the presence of ETB at 85 °C or higher. The free radicals obtained were characterized by ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC/Q-TOF MS). Gel permeation chromatography (GPC) traces of the average molecular weight of poly(MMA) (PMMA) showed a series of translations with increasing time. The average molecular weight of PMMA indicated narrow polydispersity, and a linear relationship was found between ln([M]₀/[M]) and polymerization time. These results indicated the “living” nature of the polymerization of MMA in the presence of ETB. The structure of ETB was also introduced to the end of polystyrene (PS), polyisoprene (PI), and polyisoprene-b-polystyrene (PIS) chains which were obtained by living anionic polymerization. Hence, they initiated radical polymerization of MMA as ETB-end-macroinitiators to obtain block copolymers. Thus, living anionic polymerization and this radical polymerization method were combined together to prepare block copolymers without the intermediate transformation step.     

4－N－二苯甲酮基马来酰亚胺与可聚合脂肪叔胺构成的光氧化还原体系引发甲基丙烯酸甲酯光聚合

４－Ｎ－二苯甲酮基马来酰亚胺与可聚合脂肪叔胺构成的光氧化还原体系引发甲基丙烯酸甲酯光聚合高青雨，杨更须，张福莲，张举贤（河南大学化学化工系开封４７５００１）李福绵（北京大学化学系北京１００８７１）关键词４－Ｎ－二苯甲酮基马来酰亚胺，甲基丙烯酸－Ｎ，Ｎ...     

Photoirradiated Fe-Mediated AGET ATRP of Methyl Methacrylate in the Presence of Alcohol

In this study, photoirradiated Fe-mediated AGET (activators generated by electron transfer) atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) was investigated at ambient temperature in N,N-dimethylformamide (DMF) using carbon tetrachloride as initiator, FeCl₃·6H₂O/bipyridine (Bpy) as catalyst complex, and alcohol as reducing agent. Linear semi-logarithmic plot of conversion vs. time was obtained from the kinetic experiments, and the number-average molecular weight increased linearly with monomer conversion and corresponded to the theoretic values with molecular weight distributions (M_w/M_n) as low as 1.25, which agreed with the character of controlled/living polymerization. The kinds of alcohol played an important role in photoirradiated Fe-mediated AGET ATRP of MMA. The living characteristics were demonstrated through chain extension experiment. The obtained polymer was characterized by proton nuclear magnetic resonance (NMR) and gel permeation chromatography.     

Photo-living radical polymerization of methyl methacrylate by 2,2,6,6-tetramethylpiperidine-1-oxyl in the presence of a photo-acid generator

The novel photo-living radical polymerization of methyl methacrylate (MMA) was determined using 2,2’-azobis(4-methoxy-2,4-dimethylvaleronitrile) (AMDV) and 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl (MTEMPO) in the presence of bis(alkylphenyl)iodonium hexafluorophosphate (BAI). The polymerization provided a comparatively narrow molecular weight distribution in the range of 1.4–1.7. The resulting PMMA contained no BAI fragments in its structure and had the 1-cyano-1,3-dimethyl-3-methoxybutyl radical and MTEMPO at the 1:1 molar ratio. The experimental molecular weight was in close agreement with the theoretical one when the initiator efficiency was taken into consideration. The plots of ln([MMA]₀/[MMA]) vs. time and the molecular weight of PMMA vs. the conversion and vs. the reciprocal of the initial concentration of AMDV showed linear correlations, indicating that the polymerization proceeded in accordance with a living mechanism. It was found that the polymerization had a photo-switching ability, because the polymerization was interrupted by turning off the irradiation, and then restarted by the irradiation again.