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1.
Comb-shaped graft copolymers with poly(methyl acrylate) as a handle were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization and ring-opening polymerization (ROP) techniques in three steps. First, copolymers of poly(styrene-co-chloromethyl styrene), poly(St-co-CMS), were prepared by RAFT copolymerization of St and CMS using 1-(ethoxycarbonyl)prop-1-yl dithiobenzoate (EPDTB) as RAFT agent. Second, the polymerization of MA using poly(St-co-CMS)-SC(S)Ph as macromolecular chain transfer agent produced block copolymer poly(St-co-CMS)-b-PMA. Third, cationic ring-opening polymerization of THF was performed using poly(St-co-CMS)-b-PMA/AgClO4 as initiating system to produce comb-shaped copolymers. The structures of the poly(St-co-CMS), poly(St-co-CMS)-b-PMA and final comb-shaped copolymers were characterized by 1H NMR spectroscopy and gel permeation chromatography (GPC).  相似文献   

2.
Reversible addition-fragmentation chain transfer (RAFT) polymerization of four divinyl monomers, 1,4-butanediol diacrylate (BDDA) and three poly(ethylene glycol) diacrylates (PEGDAs), were investigated under dilute conditions ([M] = 0.2-0.05 mol/L). RAFT polymerization of BDDA using a dithiocarbamate-type chain transfer agent (CTA) afforded soluble polymers, whereas a cross-linked product was obtained by conventional radical polymerization. The monomer concentration, the nature of the CTA, and the CTA/initiator ratio were found to affect the polymerization behavior and structure of the resulting polymers, which is attributed to the relative propensities for intermolecular propagating/cross-linking reactions and intramolecular cyclization. RAFT polymerizations of three PEGDAs (PEG258DA, average Mn = 258; PEG575DA, average Mn = 575; PEG700DA, average Mn = 700) having different lengths of PEG spacers (n = 3, 10, 13, respectively) were also conducted under dilute conditions. Water-soluble polymers were synthesized by one-step RAFT polymerization of PEGDAs having longer spacers (n = 10 and 13), whereas RAFT polymerization of PEGDA (n = 3) afforded polymers soluble in organic solvents. The product obtained by RAFT polymerization of PEGDA (n = 10) showed a characteristic thermoresponsive property, lower critical solution temperature (LCST), in aqueous solution.  相似文献   

3.
Jun Liu 《Polymer》2005,46(24):11133-11141
A novel trithiocarbonate, S,S′-bis(1-(((5-ethyl-2,2-dimethyl-1,3-dioxane-5-yl)methoxy)carbonyl)propyl) trithiocarbonate (CTA-H), was synthesized in the presence of the anion-exchange resin with OH form. And then it was used as the chain transfer agent in RAFT polymerizations of styrene (St), the polymers with controllable molecular weights and narrow molecular weight distributions were synthesized. After the terminal acetonide groups was deprotected in the presence of a cation-exchange resin with H+ form, the polystyrene (PSt) with two hydroxyl groups in both chain ends was easily afforded. Then it was used as macro initiator in the cation ring open polymerization (CROP) of 1,3-dioxepane (DOP), and the well-defined H-shaped block copolymers, (PDOP)2PSt(PDOP)2, were successfully prepared. The H-shaped structure was characterized by its IR, GPC and 1H NMR spectra, and also those of the hydrolysis products.  相似文献   

4.
Poly(ethylene oxide) (PEO) star microgels with a cross‐linked polystyrene core were successfully prepared by reversible addition‐fragmentation transfer polymerization of styrene (St) and divinylbenzene (DVB) with dithiobenzoate‐terminated PEO monomethyl ether (DTB‐MPEO) as macro chain transfer agent in mixtures of ethanol and tetrahydrofuran (THF). The formation of star polymers was affected by polymerization time, solvents and St:DVB:DTB‐MPEO molar ratios. Narrow polydispersed star microgels with high molecular weight were obtained under appropriate polymerization conditions. Transmission electron micrographs suggest that PEO star polymers could form nano‐size spherical micelles in mixtures of water and THF, which further demonstrates the amphiphilic nature of the star polymers. Copyright © 2006 Society of Chemical Industry  相似文献   

5.
A preliminary study on the direct controlled radical polymerization of a glycomonomer, namely 2-methacryloxyethyl glucoside (MAGlu), under reversible addition-fragmentation chain transfer (RAFT) polymerization conditions in aqueous media has been conducted. This represents the first example detailing the direct polymerization of a sugar monomer via RAFT and, significantly, has been conducted without protecting group chemistry. 4-Cyano-4-methyl-4-thiobenzoylsulfanyl butyric acid (CTP) was employed as the RAFT chain transfer agent (CTA) due to its inherent water-solubility and its applicability for methacrylic monomers. The homopolymerization displays all the characteristics of a controlled/‘living’ polymerization—linear increase in Mn with conversion, pseudo-first order kinetics, the final polymers have narrow molecular distributions and novel block copolymers can be prepared.  相似文献   

6.
Density functional theory calculations are reported for prediction of the trends in C S bond dissociation energies and atomic spin densities for radicals using S,S′‐bis(α,α′‐dimethyl‐α‐acetic acid) trithiocarbonate (TTCA) and bis(2‐oxo‐2‐phenylethyl) trithiocarbonate (TTCB) as reversible addition fragmentation chain transfer (RAFT) reagents. The calculations predict that the value of the C S bond length (1.865 Å) of TTCA is longer than that (1.826 Å) of TTCB, and TTCA is more effective for the polymerization of styrene (St) compared to TTCB as predicted by density functional theory. In photopolymerizations, pseudo‐first‐order kinetics were confirmed for TTCB‐mediated photopolymerization of St due to the linear increase of ln([M]0/[M]) up to about 28% conversion, suggesting the living characteristics behavior of the photopolymerization of St in the presence of TTCB. For both TTCA and TTCB the polydispersities change with increasing conversion in the range 1.10–1.45, typical for RAFT‐prepared (co)polymers and well below the theoretical lower limit of 1.50 for a normal free radical polymerization. In addition, the triblock copolymer polystyrene‐block‐poly(butyl acrylate)‐block‐polystyrene (PS PBA PS) was successfully prepared, with very good control over molecular weight and narrow polydispersity (Mw/Mn = 1.45), using PS S C(S) S PS as macro‐photoinitiator under UV irradiation at room temperature. This indicated that this reversible and valid strategy led to a better controlled block copolymer with defined structures. Copyright © 2007 Society of Chemical Industry  相似文献   

7.
Weidong Zhang 《Polymer》2008,49(21):4569-4575
The novel trifunctional reversible addition-fragmentation chain transfer (RAFT) agent, tris(1-phenylethyl) 1,3,5-triazine-2,4,6-triyl trithiocarbonate (TTA), was synthesized and used to prepare the three-armed polystyrene (PS3) via RAFT polymerization of styrene (St) in bulk with thermal initiation. The polymerization kinetic plot was first order and the molecular weights of polymers increased with the monomer conversions with narrow molecular weight distributions (Mw/Mn ≤ 1.23). The number of arms of the star PS was analyzed by gel permeation chromatography (GPC), ultraviolet visible (UV-vis) and fluorescence spectra. Furthermore, poly(styrene-b-N-isopropylacrylamide)3 (PS-b-PNIPAAM)3, the three-armed amphiphilic thermosensitive block copolymer, with controlled molecular weight and well-defined structure was also successfully prepared via RAFT chain extension method using the three-armed PS obtained as the macro-RAFT agent and N-isopropylacrylamide as the second monomer. The copolymers obtained were characterized by GPC and 1H nuclear magnetic resonance (NMR) spectra. The self-assembly behaviors of the three-armed amphiphilic block copolymers (PS-b-PNIPAAM)3 in mixed solution (DMF/CH3OH) were also investigated by high performance particle sizer (HPPS) and transmission electron microscopy (TEM). Interestingly, the lower critical solution temperature (LCST) of aqueous solutions of the three-armed amphiphilic block copolymers (PS-b-PNIPAAM)3 decreased with the increase of relative length of PS in the block copolymers.  相似文献   

8.
A novel vinyl ether-type RAFT agent, benzyl 2-(vinyloxy)ethyl carbonotrithioate (BVCT) was synthesized for various block copolymers via the combination of living cationic polymerization of vinyl ethers and reversible addition−fragmentation chain transfer (RAFT) polymerization. The novel BVCT–trifluoroacetic acid adduct play an important role to produce well-defined block copolymers, which is both as a cationogen under EtAlCl2 initiation system in the presence of ethyl acetate for living cationic polymerization and a RAFT agent for blocks by RAFT polymerization. The resulting polymer, poly(vinyl ether)s, by living cationic polymerization had a high number average α-end functionality (≥0.9) as determined by both 1H NMR and MALDI-TOF-MS spectrometry. In addition, this poly(vinyl ether)s worked well as a macromolecular chain transfer agent for RAFT polymerization. The RAFT polymerization of radically polymerizable monomers was conducted in toluene using 2,2′-azobis(isobutyronitrile) at 70 °C. For example, a double thermoresponsive block copolymer (MOVE61-b-NIPAM150) consisting of 2-methoxyethyl vinyl ether (MOVE) and N-isopropylacrylamide (NIPAM) was prepared via the combination of living cationic polymerization and RAFT polymerization. The block copolymer reversibly formed and deformed micellar assemblies above the phase separation temperature (Tps) of poly(NIPAM) block in water. This BVCT is not only functioned as an initiator, but also acted as a monomer. When BVCT was copolymerized with MOVE by living cationic polymerization, followed by graft copolymerization with NIPAM via RAFT polymerization, well-defined graft copolymers (MOVEn-co-BVCTm)-g-NIPAMx (n = 62–73, m = 1–9, x = 19–214) were successfully obtained. However, no micelle formed in water above Tps of poly(NIPAM) graft chain unlike the case of block copolymers.  相似文献   

9.
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   

10.
A novel reversible addition-fragmentation chain transfer (RAFT) reagent bearing triphenylamine (TPA) group, 4-diphenylamino-dithiobenzoic acid benzyl ester (DDABE), was designed and synthesized. It was used in the RAFT polymerizations of styrene (St) and methyl acrylate (MA) to prepare end-functionalized polymers. The results of the polymerization showed that the RAFT polymerizations could be well controlled using DDABE as the RAFT agent. Number-average molecular weight (Mn,GPC) increased linearly with monomer conversion, and molecular weight distributions were relatively narrow (PDI< 1.50). The results of chain-extension reaction, 1H NMR spectra and UV/Vis spectra confirmed that most of the polymers chains were end-capped by the functional triphenylamine (TPA) groups. The effect of feed molar ratios of St/DDABE/AIBN on polymerization was investigated.  相似文献   

11.
Jun Liu 《Polymer》2004,45(13):4413-4421
A novel reversible addition-fragmentation chain transfer (RAFT) agent, S,S′-bis(2-hydroxylethyl-2′-butyrate)trithiocarbonate (BHEBT), was first successfully synthesized in the presence of an anion-exchange resin with OH form, and then it was used as chain transfer agent in RAFT polymerizations of styrene or methyl acrylate, the dihydroxyl-terminated polymers with controlled molecular weights and narrow molecular weight distributions were produced, which was confirmed by GPC, 1H NMR spectra and kinetic analysis. Furthermore, these obtained telechelic polymers with trithiocarbonate group in the middle of the chains were used as macro chain transfer agents in the further RAFT polymerizations, and well-defined telechelic dihydroxyl-terminated triblock copolymers have been prepared successively. The structures were confirmed by their IR and 1H NMR spectra.  相似文献   

12.
Stable nano-TiO2/polyurethane (PU) emulsions were prepared via in situ reversible addition-fragmentation chain transfer (RAFT) emulsion polymerization of 2-hydroxyethyl acrylate (HEA)-capped PU macromonomer, using azobisisobutyronitrile (AIBN) as a radical initiator and 2-{[(butylsulfanyl)carbonothioyl]sulfanyl} propanoic acid (BCSPA) anchored onto TiO2 nanoparticles (TiO2-BCSPA) as a RAFT agent. When the molar ratio of AIBN to TiO2-BCSPA was changed from 1:3 to 1:10, the polydispersity index (PDI) of polymers in the emulsions decreased from 1.83 to 1.06, due to more effective RAFT polymerization in the emulsions. The TiO2 nanofillers were well-dispersed throughout the polymer films. The tensile strengths of the nanocomposite films were significantly enhanced due to coordination bonding between the TiO2 nanofillers and the –COOH end groups of the polymers, as evidenced by the FT-IR spectral data.  相似文献   

13.
Xiaoyan Wang 《Polymer》2005,46(10):3515-3521
The RAFT polymerization of styrene in bulk was carried out using tetraethylthiuram disulfide (TETD) as an initiator and 2-cyanoprop-2-yl 1-dithionaphthalate (CPDN) as a chain transfer agent at different temperatures. The results of the polymerization showed that TETD could initiate the RAFT polymerization of styrene in the living way. The kinetics of the polymerization showed first order. The molecular weights of the polymers increased linearly with conversions and were close to the theoretical values (Mn,th). The polydispersities of the polymers remained relatively narrow (<1.3). The structure of the polymer was characterized by 1H NMR. The result showed that there were moieties of CPDN and TETD attained at the end of the polymer. Using these double functional end capped polymers, the chain-extension experiments were successfully carried out not only in the conventional RAFT polymerization way, but also under UV irradiation.  相似文献   

14.
Durairaj Baskaran 《Polymer》2003,44(8):2213-2220
Hyperbranched polymers were synthesized using anionic self-condensing vinyl polymerization (ASCVP) by forming ‘inimer’ (initiator within a monomer) in situ from divinylbenzene (DVB) and 1,3-diisopropenylbenzene (DIPB) using anionic initiators in THF at −40 °C. The reaction of equimolar amounts of DVB and nBuLi results in the formation of hyperbranched poly(divinylbenzene) through self-condensing vinyl polymerization (SCVP). The hyperbranched polymers were invariably contaminated with small amount of gel (<15%). No gelation was observed when using DIBP with anionic initiators. The presence of monomer-polymer equilibrium in the SCVP of DIPB restricts the growth of hyperbranched poly(DIPB). The inimer synthesized from DIPB at 35 °C undergoes intermolecular self-condensation to different extent depending on the nature of anionic initiator at −40 °C. The molecular weight of the hyperbranched polymers was higher when DPHLi was used as initiator. A small amount of styrene ([styrene]/[Li+]=1) was used to promote the chain growth by inducing cross-over reaction with styrene, and subsequent reaction of styryl anion with isopropenyl groups of inimer/hyperbranched oligomer. The hyperbranched polymers were soluble in organic solvents and exhibited broad molecular weight distribution (2<Mw/Mn<17).  相似文献   

15.
KrF photoresist polymers (PASTMs) were prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization. Four (meth)acrylates with lithographic functionalities including styrene (St), 4-acetoxystyrene (AST), 2-methyl-2-adamantyl methacrylate (MAMA), and tert-butyl acrylate(TBA) were used as monomer components and 2-methyl-2-[(dodecylsulfanylthiocarbonyl) sulfanyl]propanoic acid (MDFC) was used as RAFT agent, varying the RAFT content could modulate molecular weight. Fourier-transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance (1H NMR) indicated that the synthesis was successful. Gel permeation chromatography (GPC) showed that the molecular weight decreased with the increased content of MDFC, and all the polymers possessed weight-average molecular weight below ten thousand and polydispersity less than 1.32. Thermogravimetric analysis (TGA) characterized the thermal properties, the results implied that initial thermal decomposition temperature reached 200 °C, which could satisfy the lithography process. Differential scanning calorimetry (DSC) showed that the Tg decreases with molecular weight. The RAFT polymerization kinetics plots demonstrated that the polymerization was first-order, the number-average molecular weights of the polymers with relatively low polydispersity index values increased with total monomer conversions indicating that the concentration of growing radicals was constant throughout the polymerization process. The narrow molecular weight distribution and composition uniformity of the polymers prepared by RAFT polymerization could be beneficial for lithography, after alcoholysis, lithography evaluation under KrF lithography showed that this homogeneous polymer photoresist exhibited better space and line (S/L) pattern with resolution of 0.18 μm according to the SEM image.  相似文献   

16.
Facile synthesis of poly (N,N-dimethylaminoethyl methacrylate) (PDMAEMA) star polymers on the basis of the prepolymer chains, PDMAEMA as the macro chain transfer agent and divinyl benzene (DVB) as the cross-linking reagent by reversible addition-fragmentation chain transfer (RAFT) polymerization was described. The RAFT polymerizations of DMAEMA at 70 °C using four RAFT agents with different R and Z group were investigated. The RAFT agents used in these polymerizations were dibenzyl trithiocarbonate (DBTTC), s-1-dodecyl-s''-(α,α''-dimethyl-α-acetic acid) trithiocarbonate (MTTCD), s,s''-bis (2-hydroxyethyl-2''-dimethylacrylate) trithiocarbonate (BDATC) and s-(2-cyanoprop-2-yl)-s-dodecyltrithiocarbonate (CPTCD). The results indicated that the structure of the end-group of RAFT agents had significant effects on the ability to control polymerization. Compared with the above-mentioned RAFT agents, CPTCD provides better control over the molecular weight and molecular weight distribution. The polydispersity index (PDI) was determined to be within the scope of 1.26 to 1.36. The yields, molecular weight, and distribution of the star polymers can be tuned by changing the molar ratio of DVB/PDMAEMA-CPTCD. The chemical composition and structure of the linear and star polymers were characterized by GPC, FTIR, 1H NMR, XRD analysis. For the pure Chitosan membrane, a great improvement was observed for both CO2 permeation rate and ideal selectivity of the blending composite membrane upon increasing the content of SPDMAEMA-8. At a feed gas pressure of 37.5 cmHg and 30 °C, the blinding composite membrane (Cs: SPDMAEMA-8 = 4:4) has a CO2 permeation rate of 8.54 × 10−4 cm3 (STP) cm−2∙s−1∙cm∙Hg−1 and a N2 permeation rate of 6.76 × 10−5 cm3 (STP) cm−2∙s−1∙cm∙Hg−1, and an ideal CO2/N2 selectivity of 35.2.  相似文献   

17.
AB2 3- and AB4 5-miktoarm star copolymers were prepared by combination of the anionic ring-opening polymerization (AROP) of hexamethylcyclotrisiloxane (D3) and the TEMPO-mediated radical polymerization of styrene (St). Initially, two kinds of dendritic multifunctional initiators were prepared. One has a 4-bromobutoxy group and two TEMPO-based alkoxyamines and the other has a 4-bromobutoxy group and four TEMPO-based alkoxyamines. Treatment of the multifunctional initiators with tert-butyllithium gave the corresponding lithiobutoxy derivatives, and AROP of D3 by the lithiobutoxy derivatives gave poly(D3) with Mw/Mn of 1.07-1.12. Nitroxide-mediated radical polymerization of St by the poly(D3)s at 120 °C gave AB2 3- and AB4 5-miktoarm star copolymers with Mw/Mn of 1.15-1.28. Their structures were analyzed by means of 1H NMR and SEC measurements.  相似文献   

18.
Two novel RAFT inimers, small molecule inimer 2-(methacryloyloxy)ethyl 4-cyano-4-(phenylcarbonothioylthio)pentanoate (MAE-CPP) and macro inimer PMMA-MAE-CPP were synthesized and used to prepare hyperbranched polymers via RAFT polymerization without the use of a divinyl cross-linker. The hyperbranched polymers synthesized included copolymers of MAE-CPP with styrene, copolymers of the macro inimer PMMA-MAE-CPP with styrene and the homopolymerization product of the macro inimer PMMA-MAE-CPP. The spectroscopic characteristics and polymerization kinetics of these RAFT polymers obtained under different polymerization conditions were systematically studied and the results compared with those obtained from the corresponding linear RAFT polymerizations as well as from hyperbranched polymerizations performed in the presence of a divinyl cross-linker which are reported in literature. The RAFT methodology reported here for the preparation of hyperbranched polymers is simpler than those reported previously using a divinyl cross-linker and provides good control over the hyperbranched polymers without the formation of insoluble gels.  相似文献   

19.
Well‐defined polydimethylsiloxane‐block‐polystyrene (PDMS‐b‐PS) diblock copolymers were prepared by reversible addition‐fragmentation chain transfer (RAFT) polymerization using a functional PDMS‐macro RAFT agent. The RAFT polymerization kinetics was simulated by a mathematical model for the RAFT polymerization in a batch reactor based on the method of moments. The model described molecular weight, monomer conversion, and polydispersity index as a function of polymerization time. Good agreements in the polymerization kinetics were achieved for fitting the kinetic profiles with the developed model. In addition, the model was used to predict the effects of initiator concentration, chain transfer agent concentration, and monomer concentration on the RAFT polymerization kinetics. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

20.
Different types of novel xanthates containing a vinyl ether moiety, S-benzyl O-2-(vinyloxy)ethyl carbonodithioate (Xanthate 1) and S-1-(ethoxycarbonyl)ethyl O-2-(vinyloxy)ethyl carbonodithioate (Xanthate 2) were synthesized. In particular, the Xanthate 2 enabled to design polyvinyl alcohol (PVA) stereoblock copolymer via the combination of living cationic vinyl polymerization and RAFT/MADIX polymerization. For cationic polymerization of isobutyl vinyl ether (IBVE) and tert-butyl vinyl ether (TBVE), the polymerizations were conducted under Xanthate 1-HCl adduct/SnCl4 and Xanthate 1 or 2-CF3COOH adduct/EtAlCl2 initiating system in the presence of ethyl acetate. Both systems proceeded in living polymerization fashion because the calculated Mn of both poly(IBVE) and poly(TBVE) matches with the Mn polymerized assuming that one polymer chain is formed per one molecule of the Xanthate 1 or 2. The resulting poly(TBVE) had a high number average α-end functionality as determined by MALDI-TOF-MS spectrometry. Xanthate 2 is more efficient for the following RAFT/MADIX polymerization of vinyl acetate (VAc). The RAFT/MADIX polymerization of vinyl acetate (VAc) using azobis(isobutyronitrile) (AIBN) at 60 °C was conducted using either poly(IBVE) or poly(TBVE) macro-CTA. The poly(TBVE) macro-CTAs synthesized from the Xanthate 2 were able to polymerize VAc smoothly via RAFT/MADIX polymerization, to prepare well-defined diblock copolymer, poly(TBVE)-b-poly(VAc). The resulting block copolymer was then hydrolyzed using KOH in methanol and followed by acid hydrolysis using HBr gas bubbling. The resulting polymer is inherently stereoblock like copolymer, isotactic rich PVA-b-atactic PVA (iPVA-b-aPVA). From the DSC measurement, the iPVA-b-aPVA has one glass transition at 69.5 °C and two melting points according to iPVA and aPVA at 237.9 and 198.1 °C, respectively. Thus, it can be suggested that the obtained PVA has two different geometries by the combination of living cationic polymerization and RAFT/MADIX polymerization.  相似文献   

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