PS-b-P (DMS-stat-VMS)嵌段聚合物的制备及性能

采用活性阴离子聚合方法,以仲丁基锂为引发剂,以苯乙烯、六甲基环三硅氧烷（D3）和2,4,6-三乙烯基-2,4,6-三甲基环三硅氧烷（V3）为反应单体,分步聚合制备了聚苯乙烯-b-聚（二甲基硅氧烷-stat-乙烯基甲基硅氧烷）[PS-b-P（DMS-stat-VMS）]嵌段聚合物.采用傅里叶变换红外光谱、氢核磁共振谱及凝胶渗透色谱对共聚物的化学结构、分子量及分子量分布进行了表征,并通过扫描电子显微镜、原子力显微镜及接触角等测试方法研究了共聚物各链段组分对共聚物形貌及表面亲疏水/油性的影响.结果表明,所制备的共聚物分子量分布较窄,由于各组分性能的差异而呈现出微相分离结构,同时该共聚物保留了PS-b-PDMS原有的表面性质,为设计结构多样性及性能优异的聚硅氧烷共聚物提供了新思路.     

阴离子聚合法合成PMMA-b-PMTFPS嵌段共聚物

以含缩醛官能团的有机锂为引发剂, 将甲基丙烯酸甲酯(MMA)与含氟硅氧烷单体1,3,5-三甲基-1,3,5-三(3',3',3'-三氟丙基)环三硅氧烷(F3)阴离子嵌段共聚, 获得了窄分子量分布的聚甲基丙烯酸甲酯-b-聚[甲基(3,3,3-三氟丙基)硅氧烷](PMMA-b-PMTFPS)嵌段共聚物, 并用GPC, 1H NMR, FTIR和DSC对嵌段共聚物进行了表征. 研究结果表明, 在THF中利用PMMA-OLi对F3进行阴离子开环聚合时, 单体F3浓度的选择对提高嵌段共聚物产率至关重要.     

用哈克流变仪模拟D3F反应挤出阴离子开环聚合反应

采用哈克流变仪模拟1,3,5-三甲基-1,3,5-三(3′,3′,3′-三氟丙基)环三硅氧烷(D3F)阴离子开环聚合的反应挤出试验.通过凝胶渗透色谱法(GPC)测定其绝对分子量,并通过红外光谱(FT-IR)和核磁共振氢谱(1H-NMR)表征其结构.研究表明:在促进剂乙酸乙酯作用下,120 ℃下反应4 min可得到数均分子量为2.45×105的氟硅聚合物,反应温度、时间对制备氟硅聚合物有一定的影响.     

含环三硅氮烷的星形聚硅氧烷的合成——环硅氮阴离子引发环硅氧烷开环聚合

以环三硅氮锂盐（ＤＮＬｉ３）为引发剂，成功地引发了环硅氧烷开环聚合．通过含氮量测定，利用１Ｈ、２９ＳｉＮＭＲ和ＩＲ谱以及分子量测定（ＧＰＣ）和特性粘度测试，并与模型化合物进行比较，证明所得聚合物是含环三硅氮烷的星形聚硅氧烷．研究了六甲基环三硅氮锂盐引发八甲基环四硅氧烷（Ｄ４）开环聚合的动力学，结果表明该聚合反应相对于Ｄ４为一级反应，同时也比较了不同促进剂对聚合速率的影响，ＤＭＦ对聚合速率的促进作用比ｄｉｇｌｙｍｅ大     

六甲基环三硅氧烷（D3）阴离子开环聚合机理与动力学研究

本文从聚合机理和反应动力学两方面综述了近年来六甲基环三硅氧烷（D3）的阴离子开环聚合研究进展。Frye等人提出在非极性的碳氢溶剂中会形成引发剂的的三种加成物质,在不加入促进剂的情况下不会进行D3的开环聚合,这一开环聚合机理成为随后D3阴离子开环聚合机理研究的基础,研究者采用MALDI-TOF研究聚合机理得到的结论证实了这一机理的正确性,促进剂、溶剂、引发剂的类型和聚合步骤会改变活性链末端的缔合和解缔合的平衡能力,对D3开环过程中的反咬和再分布副反应有显著影响。D3开环聚合增长速率对单体浓度为一级,不同的促进剂和引发剂会显著改变活性链末端的缔合能力,从而显著影响聚合动力学。     

环硅氧烷开环聚合研究进展

聚硅氧烷(如硅油、硅橡胶、硅树脂等)具有很多优异的性能,如耐高低温、耐紫外线辐射、耐候、低表面张力、电气绝缘、生理惰性等,已被广泛应用于航空航天、电子电器、化工、机械、建筑、交通、医疗卫生、农业等领域。聚硅氧烷制备方法主要有环硅氧烷开环聚合和硅氧烷缩聚。本文从环硅氧烷阴离子开环聚合、阳离子开环聚合和其它聚合方法等出发,较详细介绍了环硅氧烷开环聚合近年来的研究进展,并指出环硅氧烷开环聚合制备有机硅高分子材料所面临的问题。     

聚硅芳撑硅氧烷的研究(Ⅱ)——聚四甲基对硅苯撑硅氧烷的合成

本文以具有硅苯撑结构的环状有机硅氧烷--十二甲基环三对硅笨撑硅氧烷为单体,用开环聚合方法合成了聚四甲基对硅苯撑硅氧烷.选用硅醇钾催化,环单体有较高的开环聚合活性.通过IR、¹H NMR和¹³C NMR等证明了聚合物的化学结构.聚合物在空气中的热失重温度较聚二甲基硅氧烷约高110℃,因此热稳定性更好.     

环硅氧烷阴离子开环均聚及共聚研究进展

聚硅氧烷是一类典型的有机/无机杂化聚合物,具有耐高低温、优异的环境适应性等突出性能,在航空航天、国防科技等领域应用广泛.环硅氧烷单体阴离子开环聚合是制备不同链结构及功能化聚硅氧烷的重要途径,也是推动有机硅聚合物发展的重要研究领域之一.本文以阴离子开环聚合制备聚硅氧烷所涉及的环硅氧烷单体为线索,梳理了与不同化学结构环硅氧烷单体均聚及共聚相匹配的引发体系、聚合条件,以及聚合产物状态,并对相关研究工作做了论述介绍.此外,本文基于此线索对代表性研究体系做了简明罗列,便于高效检索及整体对比认知.     

硅氮负离子引发六甲基环三硅氧烷开环聚合的动力学研究

以二甲基亚砜(DMSO)或四氢呋喃(THF)作为促进剂,六苯基环三硅氮烷三锂盐(P3NLi)可以引发六甲基环三硅氧烷(D3)进行开环聚合,通过29Si-NMR谱的硅峰面积比例确定了不同反应时间D3的转化率,经过计算得到聚合反应对THF、DMSO、D3、P3NLi的反应级数,并给出了对应的动力学方程.     

聚赖氨酸为主链的牙刷状分子刷的可控合成

设计合成了溴基功能化的赖氨酸单体(Br-lys)并通过关环反应制备了对应的溴代L-赖氨酸N-羧酸酐(Br-Lys-NCA)单体.利用过渡金属引发剂Ni(COD)depe调控的NCA活性开环聚合和顺序添加单体的方法,得到了组成和结构明确的聚(ε苄氧羰基L-赖氨酸)-b-PBrLL(PZLL-PBrLL)两嵌段共聚肽.利用PZLL-b-PBrLL两嵌段共聚肽为大分子引发剂,通过ATRP引发甲基丙烯酸寡聚乙二醇酯(EGMA),合成了以聚赖氨酸为骨架的牙刷状分子刷.研究发现PZLL-PBrLL两嵌段在四氢呋喃中形成α-螺旋结构,螺旋度随着PBrLL链段的增长而降低,而PZLL-b-(PBrLL-g-PEGMA)形成部分α-螺旋构象,螺旋度随侧链PEGMA增长而减小.     

Ring‐opening Polymerization of L‐Lactide by an Anionic Cobalt(II) Aryloxide

The reaction of anhydrous CoCl₂ with NaOAr (ArO=2,4,6‐tri‐tert‐butylphenoxo) in THF at room temperature in 1:3 molar ratio afforded anionic cobalt aryloxide [Na(THF)₆][Co(OAr)₃] ( 1 ). The definite structure of this complex was characterized by X‐ray single crystal diffraction. It was found that this anionic aryloxo cobalt(II) complex could effectively initiate the ring‐opening polymerization of L‐lactide both in solution and in bulk, leading to high molecular weight poly(L‐lactide).     

Latent Olefin Metathesis Catalysts for Polymerization of DCPD

Summary: Advances in design of latent ruthenium phenylindenylidene catalysts bearing salicylaldimine ligands for ring-opening metathesis polymerization are described. The presence of the substituents in ortho position in N-aryl ring of salicylaldimine ligand has been found to be the main factor determining the catalyst stability. The best of the studied catalysts after acid activation offers activity comparable to that of the dichloride systems in ring-opening metathesis polymerization of DCPD, while maintaining very high stability in the monomer solution.     

New synthetic route of polyoxytetramethyleneglycol by use of heteropolyacids as catalyst

Polyoxytetramethyleneglycol (PTMG) can be directly prepared from tetrahydrofuran (THF) and water in the presence of heteropolyacids (HPA), without the hydrolysis step. The reaction is carried out by mixing two liquid phases: the THF phase and a heteropolyacid catalyst phase. In this reaction the molar ratio of water to a heteropolyacid (H₂O/HPA) in the catalyst phase plays an important role in the THF polymerization activity and the molecular weight of PTMG. IR spectrometric studies revealed that THF is coordinated to a heteropolyanion through either a water molecule or a proton in the catalyst phase. The latter type of coordination bings about the activation of THF capable of initiating the ring-opening polymerization even in the presence of water at a lower acid strength. The PTMG prepared by this method has a narrow molecular weight distribution (M?_w/M?_n = 1.5 or less) and a number average molecular weight of 500–2000 which are requisite for the production of polyurethane elastomers. A new polymerization mechanism named “Phase Transfer Polymerization” is proposed for elucidating a narrow molecular weight distribution.     

Synthesis and characterization of poly[styrene‐b‐methyl(3,3,3‐trifluoropropyl)siloxane] diblock copolymers via anionic polymerization

A series of narrow molecular weight distribution (MWD) polystyrene‐b‐poly[methyl(3,3,3‐trifluoropropyl)siloxane] (PS‐b‐PMTFPS) diblock copolymers were synthesized by the sequential anionic polymerization of styrene and trans‐1,3,5‐trimethyl‐1,3,5‐tris(3′,3′,3′‐trifluoropropyl)cyclotrisiloxane in tetrahydrofuran (THF) with n‐butyllithium as the initiator. The diblock copolymers had narrow MWDs ranging from 1.06 to 1.20 and number‐average molecular weights ranging from 8.2 × 10³ to 37.1 × 10³. To investigate the properties of the copolymers, diblock copolymers with different weight fractions of poly[methyl(3,3,3‐trifluoropropyl)siloxane] (15.4–78.8 wt %) were prepared. The compositions of the diblock copolymers were calculated from the characteristic proton integrals of ¹H NMR spectra. For the anionic ring‐opening polymerization (ROP) of 1,3,5‐trimethyl‐1,3,5‐tris(3′,3′,3′‐trifluoropropyl)cyclotrisiloxane (F₃) initiated by polystyryllithium, high monomer concentrations could give high polymer yields and good control of MWDs when THF was used as the polymerization solvent. It was speculated that good control of the block copolymerization under the condition of high monomer concentrations was due to the slowdown of the anionic ROP rate of F₃ and the steric hindrance of the polystyrene precursors. There was enough time to terminate the ROP of F₃ when the polymer yield was high, and good control of block copolymerization could be achieved thereafter. The thermal properties (differential scanning calorimetry and thermogravimetric analysis) were also investigated for the PS‐b‐PMTFPS diblock copolymers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4431–4438, 2005     

Novel biodegradable adaptive hydrogels: controlled synthesis and full characterization of the amphiphilic co-networks

Adaptive and amphiphilic poly(N,N-dimethylamino-2-ethyl methacrylate-graft-poly[epsilon-caprolactone]) co-networks (netP(DMAEMA-g-PCL)) were synthesized from a combination of controlled polymerization techniques. Firstly, PCL cross-linkers were produced by ring-opening polymerization (ROP) of epsilon-CL initiated by 1,4-butane-diol and catalyzed by tin(II) 2-ethylhexanoate ([Sn(Oct)2]), followed by the quantitative esterification reaction of terminal hydroxyl end-groups with methacrylic anhydride. Then, PCL cross-linkers were copolymerized to DMAEMA monomers by atom-transfer radical polymerization (ATRP) in THF at 60 degrees C using CuBr complexed by 1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA) and 2-ethyl isobutyrylbromide (EiBBr) as catalytic complex and initiator, respectively. A comprehensive study of gel formation was carried out by employing dynamic light scattering (DLS) to determine the gel point as a function of several parameters and to characterize the viscous solutions obtained before the gel point was reached. The evolution of the mean diameters was compared to a model previously developed by Fukuda and these attest to the living formation of the polymer co-network. Furthermore, we also demonstrated the reliability of ATRP for producing well-defined and homogeneous polymer co-networks by the smaller deviation from Flory's theory in terms of cross-linking density. For sake of clarity, the impact of polymerization techniques over the final structure and, therefore, properties was highlighted by comparing two samples of similar composition, but that were produced by either ATRP or thermal-initiated free-radical polymerization (FRP).     

Syntheses and radical ring-opening polymerization behavior of vinylcyclopropanone cyclic acetals having exomethylene and phenyl groups

Syntheses and radical ring-opening polymerizations of vinylcyclopropanone derivertives having cyclic six-membered acetal, exomethylene, and phenyl groups; 1-vinyl-6-methylene-4,8-dioxaspiro[2.5&]octane ( 2b ), 1-vinyl-5,7-dimethyl-6-methylene-4,8-dioxaspiro[2.5]octane ( 2c ), 1-vinyl-5-phenyl-4,8-dioxaspiro[2.5]octane ( 2d ), and 1-vinyl-5,7-diphenyl-4,8-dioxaspiro[2.5]octane ( 2e ), were carried out. The monomers were prepared by reactions of 1,1-dichloro-2-vinylcyclopropane and the corresponding diols in DMF in the presence of sodium hydride. Radical polymerizations of 2b – 2e were carried out at 60, 80, and 120°C in the presence of an appropriate initiator (3 mol % vs. monomer) in degassed sealed ampoules for 20 h. Although colorless transparent polymers (M̄_n 2300–13,500) were isolated by preparative HPLC for the most monomers, a crosslinked polymer was obtained in the case of 2b . The structures of the polymers were determined to consist of single and double ring-opening units. The content of the double ring-opened unit was 25–75% by comparison of IR spectra to a model compound. It is suggested that the double ring-opened propagating chain end is stabilized by the substituents on the cyclic acetal rings. The two-center energies of the cyclopropane ring and activation energy of ring-opening calculated by molecular orbital methods may explain the selectivity in the cleavage of the cyclopropane ring, and the degree of double ring-opening. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2501–2512, 1997     

SYTHESIS AND ANIONIC POLYMERIZATION OF 2-METHYL-2-METHOXYCARBONYL-5-METHYLENE-1, 3-DIOXOLAN-4-ONE

A new cyclic monomer, 2-methyl-2-methoxycarbonyl-5-methylene-1,3-dioxolan-4-one,was synthesized successfully. The monomer and intermediate were characterized by ~1H NMR, ~(13)CNMR, INEPT(Intensive Nuclei Enhanced by Polarization Transfer) technique, IR and elementalanalysis. Anionic polymerization of the monomer was carried out in anhydrous THF at -70℃,and 9-fluorenyllithium was used as initiator. The polymer structure was determined by IR, NMRand elemental analysis. Molecular weight of the polymer was estimated by viscosity measurementin DMSO at 30℃.     

稀土催化四氢呋喃开环聚合

1937年Meerwein首次发现Et_3O~(+BF)可催化四氢呋喃(THF)开环聚合。到目前为止,发现能使THF开环聚合的催化剂有质子酸、Lewis酸、洋离子、正碳离子等。1990年吴健等将(Acac)_3Nd-(i-Bu)_3Al-H_2O-环氧氯丙烷催化体系应用于THF聚合,发现它和(i-Bu)_3Al-H_2O-环氧氯丙烷体系具有相同的活性,这说明稀土配合物没有参与活性中心的形成。本工作发现(CF_3CO-2)3Ln(Ln=Y,La,Ce,     

SYNTHESIS AND ANIONIC POLYMERIZATION OF 2-METHYL-2-METHOXY CARBONYL-5-METHYLENE-1, 3-DIOXOLAN-4-ONE

A new cyclic monomer, 2-methyl-2-methocycarbonyl-5-methylene 1,3-dioxlan-4-one,wassynthesized successfully. The monomer and intermediate were characterized by ~1H NMR,~(13)C NMR, INEPT (Intensive Nuclei Enhanced by Polarization Transfer) technique, IR andelemental analysis. Anionic polymerization of the monomer was carried out in anhydrous THF at.70℃, and 9-fluorenyllithium was used as initiator. The polymer strucure was determined byIR, NMR and elemental analysis. Molecular weight of the polymer was estimated by viscositymeasurement in DMSO at 30℃.     

Triblock copolymers based on cyclic ethers: Preparation and properties of tetrahydrofuran and 3,3-bis(azidomethyl) oxetane triblock copolymers

Novel energetic thermoplastic elastomers (TPEs) based on tetrahydrofuran (THF) and 3,3-bis (azidomethyl) oxetane (BAMO) were prepared in this present study by cationic living polymerization. A bifunctional catalyst, triflic anhydride [(CF₃SO₂)₂)O] was selected to be an initiator for the polymerization THF and BAMO. The resulting polymers were characterized by IR, NMR, and DSC, which demonstrated that triblock copolymers with A-B-A type were formed. The polymers were indicated from thermogravimetric analysis (TGA) to have decomposed at approximately 243°C. The decomposition enthalpies were determined by DSC. These enthalpies were varied with the poly-BAMO contents of the copolymers. The synthesized polymers exhibited relatively good mechanical properties and thermoplastic characteristics at room temperature. © 1994 John Wiley & Sons, Inc.