硫氰化钠对过氧化物引发丙烯腈水溶液聚合的影响

<正> 关于硫氰化物对丙烯腈聚合的影响,早期的报道认为对过硫酸盐引发丙烯腈水溶液聚合时,硫氰化钾起阻聚作用.但丙烯腈在浓硫氰化钠水溶液中,可顺利地用偶氮双异丁腈(AIBN)、光、叔丁基过氧化氢(TBH)或TBH-醇胺引发聚合,在这些聚合反应中硫氰化钠无阻聚或缓聚作用.为了弄清硫氰化钠的影响,我们比较系统地研究硫氰化钠对丙烯腈水溶液聚合的影响.实验结果表明,其影响与所用的引发剂有关.如用TBH时,硫氰化钠起活化作用,缩短反应的诱导期,提高聚合速度与转化率,30—50℃     

较高等规度丙烯腈成纤聚合物的合成

以无水氯化镁为添加剂,考察了不同条件下的丙烯腈聚合反应,研究了溶剂种类、聚合温度和氯化镁与丙烯腈的摩尔配比对聚合反应及聚合物等规度的影响,并确定了最佳反应条件,正己烷为溶剂,偶氮二异丁腈(AIBN)为引发剂,聚合温度为60℃,氯化镁与丙烯腈的摩尔比为2∶1.在此条件下,研究了单体浓度和引发剂浓度对丙烯腈(AN)均聚合、丙烯腈/衣康酸(AN/IA)二元共聚合和丙烯腈/衣康酸/丙烯酸甲酯(AN/IA/MA)三元共聚合反应的影响,并获得了较高等规度(三单元组全同分数30.2%～55.9%)的丙烯腈均聚物和共聚物.不同等规度的丙烯腈聚合物的热分析(DSC及TGA)表明,随着聚合物等规度的提高,聚合物的环化放热峰值温度向高温区移动,而且随着聚合物等规度的提高,环化放热峰变宽.随着聚合物等规度的提高,聚合物的热稳定性变差,热失重增加,碳收率降低.     

亚硝酸钠引发丙烯腈聚合的研究

研究了亚硝酸钠引发硝酸溶液中丙烯腈的聚合反应。测得表现聚合速度 Rp=Ae~(-10,800/RT)[AN]~2.2[NaNO_2]~(0.17-1.0)[HNO_3]~(1.0-0.67 丙烯腈-丙烯酸甲酯共聚合反应中竞聚率分别是γ_An=0.96,γ_MA=1.17,表明聚合反应是按自由基机理进行。 根据聚合动力学和红外光谱分析,认为以亚硝酸钠引发硝酸溶液中丙烯腈的聚合反应与电解或金属溶蚀过程中的次级引发相同。     

4,4′-偶氮二[4-氰基戊酰(对-二甲基氨基)苯胺]引发丙烯酰胺聚合及其动力学研究

以N,N-二甲基甲酰胺(DMF)为溶剂,研究了4,4′-偶氮二[4-氰基戊酰(对-二甲基氨基)苯胺](ACPDA)为引发剂引发丙烯酰胺(AAM)的聚合行为.考察了聚合反应温度、单体浓度和引发剂浓度对聚合物分子量和聚合反应速率的影响,测定了反应级数和聚合反应的活化能.实验结果表明,ACPDA引发AAM的聚合速率方程为Rp=K[AAM]1.03[ACPDA ]0.48,聚合反应的表观活化能(Ea)为126.44kJ·mol-1.     

丙烯腈在金属镁引发下的聚合动力学

研究了金属镁在硝酸溶液中引发丙烯腈的聚合反应。实验结果表明,聚合速度与金属镁的用量无关,并且当[HNO_3]>[AN]时服从下列关系式: R_p=1.91×10~5e~(-15000/RT)[Mg]~0[AN]~(2.2)[HNO_3]~(0.45) 丙烯腈-丙烯酸甲酯的共聚试验证明,聚合反应是按自由基机理进行。     

聚(苯乙烯-丙烯酸)-氯化铜配合物催化引发丙烯腈聚合的研究

将聚(苯乙烯-丙烯酸)(PSAA)(Mw=3500)与氯化铜在异丙醇溶液中反应得到一种配位聚合物膜聚(苯乙烯-丙烯酸)-氯化铜(PSAA-Cu(Ⅱ)).研究丙烯腈(AN)在该配位聚合物膜、HSO3-和水体系(温度为55℃)催化引发作用下的聚合反应历程.AN在上述的催化引发体系中是按照自由基加聚反应历程进行聚合的,PSAA-Cu(Ⅱ)在催化引发体系中起着催化剂的配位催化作用.讨论了温度、Na2SO3浓度、AN浓度和PSAA-Cu(Ⅱ)膜用量对聚合速率、诱导时间的影响.实验结果表明,配合物PSAA-Cu(Ⅱ)膜催化引发AN聚合的诱导期为128s,反应24h后PAN产率为75.6%,Mw=2.18×104和Mn=1.12×104,多分散性系数为1.95.     

二过碘酸合银(Ⅲ)络离子氧化还原引发丙烯酰胺聚合反应动力学的研究

二过碘酸合银[Ag(Ⅲ)]在氧化还原反应中为双电子转移反应,没有中间自由基产生,不能引发丙烯腈聚合^[1,2].我们发现,Ag(Ⅲ)与不同还原剂组成氧化还原体系,在一定条件下,能引发烯类单体聚合.本文研究了Ag(Ⅲ)为氧化剂、丙烯酰胺(AM)为还原剂引发AM聚合反应的动力学,得到了聚合速率方程和表观活化能,测得了聚合物分子量M,探讨了引发机理.     

钒(V)—硫脲氧化还原体系引发丙烯腈聚合的研究 Ⅰ.聚合动力学

研究了钒(V)—硫脲氧化还原体系在硝酸溶液中引发丙烯腈的聚合反应.表观聚合速度是:R_p=2.80×10~5e~(-14000/RJ)[AN]~(2.2)[HNO_3]~(0102)[V~(5+)~(0～1/3)[TU]~(0～4/3),实验结果表明钒(V)和硫脲产生引发种是一个相当复杂的过程。     

二苯酮-苯胺体系引发丙烯腈光聚合研究

本文研究了在365nm光照下二苯酮-苯胺体系引发丙烯腈光聚合,在DMF中溶液聚合的动力学方程式为R_p∝[二苯酮]~(0.32)[苯胺]~(0.27[丙烯腈]~(1.1)。不同芳胺引发聚合的速度顺序为:N,N-二甲基苯胺>N-甲基苯胺>苯胺。考察了溶剂极性对聚合的影响,提出质子转移发生在二苯酮和苯胺的激基复合物的紧密离子对状态。聚合物端基分析表明质子转移后产生的两个自由基中主要是苯胺自由基引发聚合。     

电荷转移聚合研究——三苯基磷引发丙烯腈光聚合

研究了三苯基磷(TPP)引发丙烯腈(AN)光聚合。测定了光聚合速率 R_p与单体浓度、引发剂浓度的关系为:R_p=K[AN]~(1.49)[TPP]~(0.47)以及光聚合反应活化能E_α=6.16千卡/摩尔,从激发态电荷转移机制,讨论了引发聚合机理。     

Steady-state kinetics during initial stages of radical bulk polymerization of acrylonitrile

The bulk polymerization of acrylonitrile with azobisisobutyronitrile as initiator and FeCl₃ as terminator was studied at 60°C. It was found that the reaction proceeds like solution polymerization and does not exhibit the familiar autoacceleration found in bulk polymerizations. It was concluded that a steady-state condition of growing radical chains exists. Initial rates, to approximately 3% conversion, were measured dilatometrically and were found to be proportional to the ratio of the initiator to terminator concentration, where this ratio is smaller than 3 : 1 and are due to the predominance of the FeCl₃ monoradical termination mechanism. On increasing the ratio of initiator to FeCl₃, the usual biradical termination mechanism becomes important as well. Assuming that the ratio of propagation constant to termination constant in this work is similar to the knwon ratio in DMF solution, a monomer “effective” concentration in the bulk of about 20% of the nominal concentration of pure acrylonitrile (14.38 mole/l. at 60°C) can be calculated. This result is interpreted by a molecular mechanism for the bulk polymerization of acrylonitrile.     

Polymerization of n-Hexyl Isocyanate Initiated by Novel Rare Earth Tris （2,6-di-tert-butyl-4-methylphenolate）

The polymerization of n-hexyl isocyanate (HNCO) was carried out in the presence of a novel single initiator, rare earth tris (2,6-di-tert-butyl-4-methylphenolate) [Ln(OAr)3]. The influences of reaction conditions such as the monomer concentration, the polymerization temperature and time, and the types of solvents on the polymerization of HNCO were studied. Polymerizations of phenyl, i-propyl, p-tolyl, n-butyl and n-octyl isocyanates with La(OAr)3 were also examined.     

RING-OPENING POLYMERIZATION OF 1,4-DIOXAN-2-ONE INITIATED BY LANTHANUM TRIS( 2,6-DI- TERT-B UTYL-4-METHYLPHENOLATE)

The ring-opening polymerization of 1,4-dioxan-2-one (PDO) was carried out by lanthanum tris(2,6-di-tert-butyl-4-methylphenolate) (La(OAr)3) as novel single component initiator. The influences of polymerization reaction temperature and the molar ratio of monomer to initiator on the monomer conversion and molecular weight of poly(1,4-dioxan-2-one) (PPDO) were explored. PPDO with high viscosity average molecular weight of 1.95 × 105 can be prepared at 40℃ when [PDO]/ [La(OAr)3] molar ratio was 800. Mechanism investigation shows that the polymerization proceeds through a "coordinationinsertion" mechanism with selective rupture of acyl-oxygen bond of PDO.     

RING-OPENING POLYMERIZATION OF 1,4-DIOXAN-2-ONE INITIATED BY LANTHANUM TRIS（ 2,6-DI-TERT-BUTYL-4-METHYLPHENOLATE）

The ring-opening polymerization of 1,4-dioxan-2-one （PDO） was carried out by lanthanum tris（2,6-di-tert-butyl-4- methylphenolate） （La（OAr）3） as novel single component initiaLor. The influences of polymerization reaction temperature and the molar ratio of monomer to initiator on the monomer conversion and molecular weight of poly（1,4-dioxan-2-one） （PPDO） were explored. PPDO with high viscosity average molecular weight of 1.95×10^5 can be prepared at 40℃ when [PDO]/ [La（OAr）3] molar ratio was 800. Mechanism investigation shows that the polymerization proceeds through a ＂coordination- insertion＂ mechanism with selective rupture of acyl-oxygen be,nd of PDO.     

Monoaryloxo ytterbium(III) chlorides supported by β‐diketiminato ligands as novel initiators for the living ring‐opening polymerization of ε‐caprolactone

Ring‐opening polymerization of ε‐caprolactone (ε‐CL) was carried out using β‐diketiminato‐supported monoaryloxo ytterbium chlorides L¹Yb(OAr)Cl(THF) (1) [L¹ = N,N′‐bis(2,6‐dimethylphenyl)‐2,4‐pentanediiminato, OAr = 2,6‐di‐tert‐butylphenoxo‐], and L²Yb(OAr′)Cl(THF) (2) [L² = N,N′‐bis(2,6‐diisopropylphenyl)‐2,4‐pentanediiminato, OAr′ = 2,6‐di‐tert‐butyl‐4‐methylphenoxo‐], respectively, as single‐component initiator. The influence of reaction conditions, such as polymerization temperature, polymerization time, initiator, and initiator concentration, on the monomer conversion, molecular weight, and molecular weight distribution of the resulting polymers was investigated. Complex 1 was well characterized and its crystal structure was determined. Some features and kinetic behaviors of the CL polymerization initiated by these two complexes were studied. The polymerization rate is first order with respect to monomer. The M_n of the polymer increases linearly with the increase of the polymer yield, while polydispersity remained narrow and unchanged throughout the polymerization in a broad range of temperatures from 0 to 50 °C. The results indicated that the present system has a “living character”. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1147–1152, 2006     

Preparation and polymerization mechanism of dihydroxy-capped PCL,poly(CL-b-PEG-b-CL) and poly(DTC-b-CL-b-DTC)

PCL possesses a wide range of medical applications, such as tissue engineering and controlled drug release, because of its good biodegradability and miscibility. In order to extend the use of PCL, researchers have been exploring its structural and chemica…     

Copolymerisation radiochimique du styrene avec l'acrylonitrile en solution

The radiation-initiated copolymerization of styrene and acrylonitrile was investigated at 20° in dimethylformamide (DMF) and in benzylalcohol solutions. The compositions of the copolymers were only slightly affected by these polar solvents. The influence of temperature on the copolymerization in DMF solutions was studied in greater detail. It was found that the acrylonitrile content in the copolymer obtained at -78° drastically increased as a result of an anionic polymerization of acrylonitrile. Fractional precipitation of the products obtained at -78° showed that they were not mixtures of polymers but were block copolymers containing long sequences of acrylonitrile units. This copolymer is assumed to arise as a result of the simultaneous growing of the two ends of a primary radical-ion, acrylonitrile adding to one end by an anionic mechanism while the free radical end initiates a random copolymerization of styrene and acrylonitrile. The anionic contribution to the over-all process was established. The anionic homopolymerization of acrylonitrile was studied in DMF, toluene and their mixtures. The rate was found to exhibit a maximum for 20% acrylonitrile in DMF. It was further noticed that significant amounts of DMF could be replaced by toluene or styrene without affecting the rate. The reduction in rate in more concentrated monomer solutions was attributed to an autoinhibition of acrylonitrile in its anionic polymerization.     

Anionic Polymerization of Z,Z-2,4Hexadienedinitrile

Abstract

Z,Z-2,4-Hexadienedinitrile, synthesized by the oxidative cleavage of o-phenylenediamine, was found to undergo anionic polymerization with n-BuLi in DMF at room temperature or below. The polymerization behavior appears to be similar to that of acrylonitrile polymerization using n-BuLi as initiator. Infrared and NMR analysis of the polymer indicate the presence of both 1,4 and 1,2 linkages, with the latter predominating.     

Reverse Atom Transfer Radical Polymerization of Acrylonitrile Catalyzed by FeCl3/Lactic Acid

Reverse atom transfer radical polymerization (RATRP) of acrylonitrile (AN) was carried out using azobisisobutyronitrile (AIBN) as initiator, ferric trichloride anhydrous (FeCl₃)/lactic acid (LA) as catalyst system; a ratio of FeCl₃/LA was 1:2 gave the best control. RATRP of AN with N,N-dimethylformamide (DMF) as solvent gave the moderate polymerization rate and the narrowest polydispersity index (PDI). When FeCl₃ was replaced by CuBr₂, RATRP of AN showed a longer induction period. When Cu was added to the CuBr₂-based catalyst system, the induction period was reduced. ¹H-NMR spectra of PAN verified the possibility of controlled/living polymerization for future chain extension.     

Poly(vinyl acetate) as a template for the radical polymerization of acrylonitrile

The template polymerization of acrylonitrile (AN) along with atactic-poly(vinyl acetate) of M _v (47,090), at 60°C for 120 min in dimethyl formamide (DMF) has been studied dilatometrically to study the effects of template, monomer, and initiator (benzoyl peroxide) concentration upon kinetics. Viscometric measurements showed that complexation between at-PVAc and PAN was maximum when template/polymer ratio was 1:1 and time required for complete complexation was 15 min. The overall energy of activation was 57.76 and 77.01 kJ/mol in the presence and absence of, PVAc, respectively. The overall system follows mechanism I, i.e., the monomer molecules get adsorbed on the surface of the template macromolecules and then propagation proceeds.