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1.
Cationic polymerizations of p-methylstyrene (pMS) with H2O/AlCl3/triphenylamine (TPA) or triethylamine (TEA) initiating system were carried out in mixed solvents of n-hexane and dichloromethane at ?80 ~ ?50 °C. The effects of TPA or TEA concentration, solvent polarity, polymerization temperature and time on monomer conversion, number-average molecular weight (Mn), molecular weight distribution (MWD, Mw/Mn), stereoregulatity and crystallinity of poly(p-methylstyrene) (PpMS) were investigated. The stereospecific cationic polymerization of p-methylstyrene could be achieved and high molecular weight (Mn = 116,000 ~ 436,000 g mol?1) polymers with isotactic-rich segments (more than 75% of meso dyad) along macromolecular chains could be successfully synthesized. A possible mechanism for stereospecific cationic polymerization of pMS was proposed. The propagation proceeded via the dominant back-side attack and insertion of monomer from the growing ion paired species. The steric course of propagation was mainly determined by the tightness of the growing ion paired species and steric hindrance in counteranion. The resulting isotactic-rich PpMS could form crystal morphology with 10 ~ 30 μm in size by flow-induced crystallization under pressure at 180 °C. A possible model for the aligning mechanism was sketched to describe crystallization and to explain the multi-melting peaks and lower glass transition temperatures of PpMS. This is the first example of stereospecific cationic polymerization of p-methylstyrene to get crystallizable polymers with such high molecular weights and isotacticity. 相似文献
2.
Thermal polymerization of methyl (meth)acrylate (MMA) was carried out using 2-cyanoprop-2-yl-1-dithionaphthalate (CPDN) and cumyl dithionaphthalenoate (CDN) as chain transfer agents. The kinetic study showed the existence of induction period and rate retardation, especially in the CDN mediated systems. The molecular weights of the polymers increased linearly with the monomer conversion, and the molecular weight distributions (Mw/Mns) of the polymers were relatively narrow up to high conversions. The maximum number-average molecular weights (Mns) reached to 351?900 g/mol (Mw/Mn = 1.47) and 442?400 g/mol (Mw/Mn = 1.29) in the systems mediated by CPDN and CDN, respectively. Chain-extension reactions were also successfully carried out to obtain higher molecular weight PMMA and PMMA-block-polystyrene (PMMA-b-PSt) copolymer with controlled structure and narrow Mw/Mn. Thermal polymerization of methyl acrylate (MA) in the presence of CPDN, or benzyl (2-phenyl)-1-imidazolecarbodithioate (BPIC) also demonstrated “living”/controlled features with the experimented maximum molecular weight 312?500 g/mol (Mw/Mn = 1.57). The possible initiation mechanism of the thermal polymerization was discussed. 相似文献
3.
Jieai Li Zhengbiao Zhang Xiulin Zhu Jian Zhu Zhenping Cheng Wenjian Xu 《Polymer Bulletin》2010,64(1):1-13
The stable free radical polymerizations of styrene were investigated with five 4-sulphonate-2,2,6,6-tetramethylpiperidine-N-oxyl stable radicals as mediators and benzoyl peroxide (BPO) as initiators at 125 °C. The results indicated that the polymerizations
proceeded in a “living”/controlled manner, i.e., the polymerization rates were first-order with respect to the monomer concentrations,
molecular weights increased linearly with conversions and the molecular weight distributions were relatively low (M
w/M
n = 1.2–1.4), 1H NMR analysis of the polymer chain-ends and successful chain extensions. The polymerization rates were faster than that of
4-hydroxyl-2,2,6,6-tetramethylpiperidine-N-oxyl (OH-TEMPO) mediated ones. The effects of steric interference of different substitute groups at four-position of 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO), the molar ratios of stable radical to BPO and the temperature on the polymerizations were investigated. 相似文献
4.
Primary amine functionalized polystyrenes were prepared in quantitative yields by atom transfer radical polymerization using the adduct of 1‐(bromoethyl)benzene with 1‐(4‐aminophenyl)‐1‐phenylethylene as initiator for styrene polymerization in the presence of a copper(I) bromide/N,N,N′,N′,N″‐pentamethyldiethylenetriamine catalyst system. The polymerizations proceeded via a controlled free radical polymerization process to afford quantitative yields of the corresponding primary amine functionalized polystyrenes with predictable molecular weights (Mn = 2 × 103 to 10 × 103 g mol?1), relatively narrow molecular weight distributions (Mw/Mn = 1.03–1.49), well defined chain‐end functionalities and initiator efficiencies as high as 0.92. The polymerization process was monitored by gas chromatographic analysis. The primary amine functionalized polymers were characterized by thin layer chromatography, size exclusion chromatography, potentiometry and spectroscopy. Experimental results are consistent with quantitative functionalization via the 1,1‐diphenylethylene derivative. Polymerization kinetic measurements show that the polymerization reaction follows first order rate kinetics with respect to monomer consumption and the number average molecular weight increases linearly with monomer conversion. © 2003 Society of Chemical Industry 相似文献
5.
Two novel dithiocarbamates [2‐Y‐benzoimidazole‐1‐carbodithioic acid benzyl esters: Y = methyl (1b) or phenyl (1c)] were synthesized and successfully used in the reversible addition–fragmentation chain transfer (RAFT) polymerization of styrene in bulk with thermal initiation. The effects of the temperatures and concentration ratios of the styrene and RAFT agents on the polymerization were investigated. The results showed that the polymerization of styrene could be well controlled in the presence of 1b or 1c. The linear relationships between ln([M]0/[M]) and the polymerization time (where [M]0 is the initial monomer concentration and [M] is the monomer concentration) indicated that the polymerizations were first‐order reactions with respect to the monomer concentration. The molecular weights increased linearly with the monomer conversion and were close to the theoretical values. The molecular weight distributions [weight‐average molecular weight/number‐average molecular weight (Mw/Mn)] were very narrow from 5.3% conversion up to 94% conversion (Mw/Mn < 1.3). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 560–564, 2006 相似文献
6.
In this study, an addition-fragmentation chain transfer agent bearing dithioester group is synthesized and applied to conventional dispersion photopolymerization of styrene in ethanol medium in the presence of poly(N-vinylpyrrolidone) stabilizer with varying amounts of the RAFT agent and optionally with conventional initiator, azobisisobutyronitril (AIBN) at various temperatures. Monomer conversion, molecular weight evolution, polydispersity index (PDI), and final particle sizes are measured. The PDI of the formed polymer is between 1.5 and 2.5 in the presence of RAFT agent. Higher concentration of RAFT agent or elevated temperature leads to the acceleration of the polymerization rate resulting in fast conversion, and reducing molecular weight and PDI. Stable polystyrene beads above 1 μm in diameter are successfully prepared by means of RAFT method applied in dispersion polymerization. The weight average particle sizes are between 1.08 and 2.04 μm, and the uniformity (Dw/Dn) is ranged from 1.26 to 2.51. 相似文献
7.
2‐(1‐Bromoethyl)‐anthraquinone (BEAQ) was successfully used as an initiator in the atom transfer radical polymerization of styrene with CuBr/N,N,N′,N′,N″‐pentamethyldiethylenetriamine as the catalyst at 110°C. The polymerizations were well controlled with a linear increase in the molecular weights (Mn's) of the polymers with monomer conversion and relatively low polydispersities (1.1 < weight‐average molecular weight (Mw)/Mn < 1.5) throughout the poly merizations. The resultant polystyrene thus possessed one chromophore moiety (2‐ethyl‐anthraquinone) at the α end and one bromine atom at the ω end, both from the initiator BEAQ. The intensity of UV absorptions of the resultant polymers decreased with increasing molecular weights of the polymers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2081–2085, 2006 相似文献
8.
Two monodisperse graft copolymers, poly(4‐methylstyrene)‐graft‐poly(tert‐butyl acrylate) [number‐average molecular weight (Mn) = 37,500, weight‐average molecular weight/number‐average molecular weight (Mw/Mn) = 1.12] and polystyrene‐graft‐poly(tert‐butyl acrylate) (Mn = 72,800, Mw/Mn = 1.12), were prepared by the atom transfer radical polymerization of tert‐butyl acrylate catalyzed with Cu(I) halides. As macroinitiators, poly{(4‐methylstyrene)‐co‐[(4‐bromomethyl)styrene]} and poly{styrene‐co‐[4‐(1‐(2‐bromopropionyloxy)ethyl)styrene]}, carrying 40% of the bromoalkyl functionalities along the chain, were used. The dependencies of molecular parameters on monomer conversion fulfilled the criteria for controlled polymerizations. In contrast, the dependencies of monomer conversion versus time were nonideal; possible causes were examined. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2930–2936, 2002 相似文献
9.
Reverse iodine transfer polymerizations (RITP) of 2‐h‐ydroxyethyl acrylate (HEA) were performed in N,N‐dimethylformamide at 75°C using AIBN as initiator. Poly(2‐hydroxyethyl acrylate) (PHEA) with Mn = 3300 g mol?1 and Mw/Mn <1.5 were obtained. Homopolymerization of styrene in RITP was also carried out under similar conditions using toluene as solvent. The resulting iodo‐polystyrene (PS‐I) with (Mn, SEC = 607 g mol?1, polydispersity index (PDI) = 1.31) was used as a macroinitiator for the synthesis of amphiphilic block copolymers based on HEA with controlled well‐defined structure. Poly(styrene‐b‐2‐hydroxyethyl acrylate) (PS‐b‐PHEA) with Mn = 13,000 g mol?1 and polydispersity index (Mw/Mn) = 1.4 was obtained, copolymer composition was characterized using 1H‐NMR and FTIR, whereas SEC and gradient HPLC were used to confirm the formation of block copolymer and the living character of polymer chains. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
10.
Free radical polymerization of styrene in supercritical CO2 requires addition of a surfactant to produce polystyrene (PS) in high conversion and molecular weight with well‐defined particle sizes. In this work, we examined a new stabilizer that can provide effective stabilization for the polymerization of styrene. A commercially available poly(dimethylsiloxane) macromonomer has been employed as a stabilizer for dispersion polymerization of PS in scCO2. The reactions were conducted in a 225‐mL stainless steel autoclave over the temperature range 60–80°C and under pressures of 1,500 to 3,000 psi. After 2–12 h of polymerization, the conversion determined by gravimetrical method was between 20 and 80%. These preliminary results suggest that this macromonomer offers satisfactory stabilization for the styrene system. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 545–549, 2004 相似文献
11.
Preeyanuch Sangtrirutnugul Kritdikul Wised Purmpoon Maisopa Nisalak Trongsiriwat Pramuan Tangboriboonrat Vichai Reutrakul 《Polymer International》2014,63(10):1869-1874
The tripodal ‘click’ compound tris(4‐trimethylsilylmethyl‐1,2,3‐triazolylmethyl)amine (TTTA) was prepared and investigated as a ligand for copper‐catalysed single‐electron transfer living radical polymerization of methyl methacrylate (MMA). Bulk polymerizations catalysed by Cu0/CuBr2/TTTA with a molar ratio of [MMA]0/[ethyl‐2‐bromoisobutyrate]0/[CuBr2]0/[TTTA]0 = 200:2:1:1 and a 1.0 × 1.0 cm2 Cu0 sheet were fast and well controlled (76% conversion with Mw/Mn = 1.19 after 3.5 h). Greater amounts of added air generally gave slower polymerizations although Mw/Mn remained low (<1.3) even when the polymerization was carried out under aerobic conditions. Decreasing initial concentrations of the Cu0/CuBr2/TTTA catalyst system or polymerization temperatures also resulted in slower polymerizations and yielded polymers with broader dispersity. Kinetic studies in the temperature range 40–90 °C revealed an apparent activation energy of 22.6 kJ mol?1. © 2014 Society of Chemical Industry 相似文献
12.
Summary
tert-Butoxybenzenes including the 4-substituted derivatives of anisole, toluene and p-chlorobenzene have been synthesized and studied as initiators in combination with TiCl4 for polymerization of isobutylene (IB) in CH2Cl2/methylcyclohexane (MeCHx) solvent mixtures at -78°C. Living polymerizations with slow initiation were observed by the allmonomer-in (AMI) and incremental monomer addition (IMA) techniques, and polymers with narrow molecular weight distribution (MWD) (Mw/Mn>1.1) were obtained under certain conditions. Aging of the initiating system prior to charging the monomer does not improve the initiating efficiency. It has been found that the initiating efficiency can be increased by increasing the solvent polarity, however, the relative volume of CH2Cl2 is limited in order to avoid polymer precipitation and bimodal MWD. 相似文献
13.
Poly(styrene)‐poly(lactide) (PS‐PLA), poly (tert‐butyl styrene)‐poly(lactide) (PtBuS‐PLA) diblocks, and poly(tert‐butyl styrene)‐poly(styrene)‐poly(lactide) (PtBuS‐PS‐PLA) segmented and tapered triblocks of controlled segment lengths were synthesized using nitroxide‐mediated controlled radical polymerization. Well‐defined PLA‐functionalized macromediators derived from hydroxyl terminated TEMPO (PLAT) of various molecular weights mediated polymerizations of the styrenic monomers in bulk and in dimethylformamide (DMF) solution at 120–130°C. PS‐PLA and PtBuS‐PLA diblocks were characterized by narrow molecular weight distributions (polydispersity index (Mw/Mn) < 1.3) when using the PLAT mediator with the lowest number average molecular weight Mn= 6.1 kg/mol while broader molecular weight distributions were exhibited (Mw/Mn = 1.47‐1.65) when using higher molecular weight mediators (Mn = 7.4 kg/mol and 11.3 kg/mol). Segmented PtBuS‐PS‐PLA triblocks were initiated cleanly from PtBuS‐PLA diblocks although polymerizations were very rapid with PS segments ~ 5–10 kg/mol added within 3–10 min of polymerization at 130°C in 50 wt % DMF solution. Tapering from the PtBuS to the PS segment in semibatch mode at a lower temperature of 120°C and in 50 wt % DMF solution was effective in incorporating a short random segment of PtBuS‐ran‐PS while maintaining a relatively narrow monomodal molecular weight distribution (Mw/Mn ≈ 1.5). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008 相似文献
14.
Atom transfer radical polymerization of lauryl methacrylate (LMA) was carried out in the presence of various ligands using ethyl-2-bromoisobutyrate as initiator and CuBr as catalyst in toluene at 95 °C. The ligands used were 2,2′-bipyridyl,4,4′-dimethyl-2,2′-bipyridyl, N,N,N′,N′,N″-pentamethyldiethylenetriamine (PMDETA) and N-(n-propyl)-2-pyridylmethanimine (PPMI). Controlled polymerization was observed with PMDETA and PPMI ligands and poly(LMA)s with narrow molecular weight distribution (MWD) (Mw/Mn≤1.2) were obtained. The first-order time-conversion plot showed the presence of termination in the presence of PMDETA. A linear first-order time-conversion plot with a small induction period (∼10 min) was observed in the presence of PPMI ligand. Di-block copolymers of LMA and methylmethacrylate with controlled molecular weight and narrow MWDs were synthesized via sequential monomer addition. 相似文献
15.
Summary Living carbocationic polymerization of styrene (St) has been achieved by the use of the 1(p-methylphenyl)ethyl acetate (pMePhEtOAc)·BCl3 complex in CH3Cl solvent at –30°C using both the IMA and AMI techniques. The living nature of the polymerizations has been demonstrated by linear Mn versus WPSt (weight of polystyrene) plots passing through the origin and horizontal N (moles of PSt) versus WPSt plots starting at N=Io (the number of moles of initiator used). The molecular weight distribution MWD of the PSts is broad (Mw/Mn=~5–6) due to slow initiation and/or slow exchange between dormant and active species relative to propagation. The structure of the ester initiator strongly affects the rate and outcome of living polymerization, e.g., cumyl acetate (CumOAc), cumyl propionate (CumOPr), and 2,4,6-trimethylphenylethyl acetate (TMePhEtOAc), do not lead to truly living St polymerizations. The findings with the latter esters is explained in terms of a two path process comprising a slow living polymerization and a faster conventional cationic chain reaction. With phenylethyl acetate (PhEtOAc) living polymerization is achieved, however, initiation (cation generation) is slow. Forced termination by pyridine or methanol, or heating to ambient temperature leads to-CH2CH(C6H5)Cl end groups. 相似文献
16.
The controlled polymerization of vinyl chloride (VC) with tert-butyllithium (tert-BuLi) was investigated. The polymerization of VC with tert-BuLi at −30 °C proceeded to give a high molecular weight polymer in good yield. In the polymerization of VC −30 to 0 °C under nearly bulk, the relationship between the Mn of polymers and polymer yields gave a straight line passed through the origin, but the Mw/Mn of PVC was not narrow. When CH2Cl2 was used as polymerization solvent, the Mn of PVC increased with the polymer yield, and the Mw/Mn of 1.25 was obtained. Structure analysis of the resulting polymers indicates that the main chain structure could be regulated in the polymerization of VC with tert-BuLi. Accordingly, a control of molecular weight of polymer and main chain structure is possible in the polymerization of VC with tert-BuLi. 相似文献
17.
Assessment of kinetics of photoinduced Fe‐based atom transfer radical polymerization under conditions using modeling approach
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Kinetic insight into photoinduced Fe‐based atom transfer radical polymerization (ATRP) involving monomer‐mediated photoreduction was performed by modeling approach for the first time. Preliminary numerical analysis of number‐average molar mass (Mn) derivation in this specific system was given. Simulation results provided a full picture of reactant concentration and reaction rate throughout the entire polymerization. Methyl 2,3‐dibromoisobutyrate (MibBr2) generated from methyl methacrylate (MMA)‐mediated photoreduction as the leading factor for the deviation of Mn from theoretical value was confirmed by reaction contributions in α‐bromophenylacetate (EBPA) containing system. Reasonable predictions were made with respect to the polymerizations under a variety of initial conditions. Results show that increasing light intensity will shorten transition period and increase steady state polymerization rate; decreasing catalyst loading will cause the decrease in polymerization rate and Mn deviation; varying initiation activity will slightly increase the time to attain steady state of dispersity (Mw/Mn) evolution and enormously change the fraction of reaction contributions; increasing targeted chain length will extend transition period, decrease steady state polymerization rate, increase Mn deviation degree with same reaction contributions, and decrease the time to attain the steady state of Mw/Mn. The numerical analysis presented in this work clearly demonstrates the unique ability of our modeling approach in describing the kinetics of photoinduced Fe‐based ATRP of MMA. © 2017 American Institute of Chemical Engineers AIChE J, 2017 相似文献
18.
The recently developed living free-radical polymerization system, atom transfer radical polymerization using activators generated by electron transfer for atom transfer radical polymerization (AGET ATRP), was used for methyl methacrylate (MMA) polymerization in the presence of a limited amount of air, using a novel catalyst system based on iron (FeCl3) complexes with iminodiacetic acid (IDA) and using ascorbic acid (VC) as a reducing agent. The kinetics of AGET ATRPs of MMA with different amounts of VC in the presence of air was investigated. The results of the polymerizations demonstrated the features of “living”/controlled free-radical polymerization such as the number-average molecular weights increasing linearly with monomer conversion and narrow molecular weight distributions (Mw/Mn = 1.31–1.44). 相似文献
19.
Novel triazole-based aluminum complex {O,O′-[4,5-P(O)Ph2tz]-AlMe2 was studied as the catalyst for the ring-opening polymerization of caprolactone (ε-CL) in chlorobenzene. In the presence
of methanol, isopropanol, and bifunctional poly(ethylene glycol), the catalytic system produced polymers with high conversion
(81–85 %) but broader distribution (M
w/M
n = 1.5–1.8). The system of catalyst and benzyl alcohol produced relative monodisperse PCLs (M
w/M
n ~ 1.2) with defined molecular weight at 1/1ratio, 60 °C and an initial concentration of ε-CL equal to 0.5 mol/L. 相似文献
20.
Summary Micelle-forming sodium 6-acrylamidocaproate (Na 6-AAC) and sodium 11-(N-methyl acrylamido)undecanoate (Na 11-MAAU) were synthesized and polymerized in aqueous solutions. The polymerization was very rapid and it followed first-order kinetics with respect to the monomer and one-half order to K2S2O8. The activation energy for the polymerization of Na 11-MAAU (62.3 kJ/mol) was much lower than that for Na 6-AAC (98.1 kJ/mol). The ¯Mw. for the former was around one million and it was only one-third of that for the latter. Their MWD (¯Mw/¯Mn - 1.5) are relatively narrow. The relationships between intrinsic viscosity []o and ¯Mw for these polysurfactants have also been established. 相似文献