共查询到20条相似文献,搜索用时 15 毫秒
1.
Madhubhashini Maddumaarachchi Frank D. Blum 《Journal of Polymer Science.Polymer Physics》2014,52(10):727-736
Adsorbed poly(ethylene‐stat‐vinyl acetate) (PEVAc) on fumed silica was studied using temperature‐modulated differential scanning calorimetry (TMDSC) and FT‐IR spectroscopy. The properties of the copolymers were compared with poly(vinyl acetate) (PVAc) and low density polyethylene (LDPE) as references. TMDSC analysis of the copolymer‐silica samples in the glass transition region was complicated for the copolymers because of the ethylene crystallinity. Nevertheless, examination of the glass transition region for small adsorbed amounts of these copolymers indicated the presence of tightly‐ and loosely‐bound polymer segments, similar to other polymers which have an attraction to silica. Compared with bulk polymers with the same composition, the tightly‐bound polymers showed an increased glass transition temperature (Tg) and a loosely‐bound fraction with a lower Tg than bulk. FT‐IR spectra of the surface copolymers indicated that the fraction of bound carbonyls (p) increased as the fraction of vinyl acetate in the copolymers decreased, consistent with the notion that the carbonyls from vinyl acetate preferentially find their way to the silica surface. Spectra from samples with different adsorbed amounts of polymer were used to obtain the amount of bound polymer (Mb) and the ratio of molar absorption coefficients of bound carbonyls to free carbonyls (X). The copolymers had very large p values (up to 0.8) at small adsorbed amounts and dependent on the composition of the polymer. However, an analysis of the bound fractions, based on only the vinyl acetate groups, superimposed the data, suggesting that the ethylene units simply dilute the vinyl acetate groups in the surface polymer. The sample with the smallest fraction of vinyl acetate did not show this behavior and may be considered to be “carbonyl poor.” © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 727–736 相似文献
2.
《Surface and interface analysis : SIA》2005,37(1):53-61
Polyatomic primary ions offer low penetration depth and high damage removal rates in some polymers, facilitating their use in the molecular depth profiling of these polymers by secondary ion mass spectrometry (SIMS). This study is the second in a series of systematic characterizations of the effect of polymer chemistry on degradation under polyatomic primary ion bombardment. In this study, time‐of‐flight SIMS (ToF‐SIMS) was used to measure the damage of ~90 nm thick spin‐cast poly(methyl methacrylate), poly(n‐butyl methacrylate), poly(n‐octyl methacrylate) and poly(n‐dodecyl methacrylate) films under extended (~2 × 1014 ions cm?2) 5 keV SF5+ bombardment. The degradation of the poly(n‐alkyl methacrylates) were compared to determine the effect of the length of the alkyl pendant group on their degradation under SF5+ bombardment. The sputter rate and stability of the characteristic secondary ion intensities of these polymers decreased linearly with alkyl pendant group length, suggesting that lengthening the n‐alkyl pendant group resulted in increased loss of the alkyl pendant groups and intra‐ or intermolecular cross‐linking under SF5+ bombardment. These results are partially at variance with the literature on the thermal degradation of these polymers, which suggested that these polymers degrade primarily via depolymerization with minimal intra‐ or intermolecular cross‐linking. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
3.
Suriyaphongse Kulkeratiyut Suntree Kulkeratiyut Frank D. Blum 《Journal of Polymer Science.Polymer Physics》2006,44(15):2071-2078
The fraction of directly‐bound carbonyls of surface‐adsorbed poly(methyl methacrylate) (PMMA) was determined using transmission Fourier‐transform infrared (FTIR) spectroscopy. The small size of the silica used allowed these measurements to be made directly in the transmission mode from dried casts deposited on KBr salt plates. Curve fitting of the carbonyl‐stretching region allowed the estimation of both the relative amounts and also the relative ratio of the absorption coefficients for the free and bound carbonyls. The bound‐carbonyl fractions were found to vary smoothly from 0.3 to 0.1 for adsorbed amounts from 0.5 to 1.8 mg of PMMA/m2. The bound fractions depended primarily on the adsorbed amount of polymer. Only very small, perhaps even negligible, direct effects of the solvent composition (toluene vs. benzene/acetonitrile) or molecular mass (32 to 420 kg/mol) were observed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2071–2078, 2006 相似文献
4.
《Journal of Polymer Science.Polymer Physics》2018,56(1):89-96
The effects of adsorption of poly(lauryl methacrylate) (PLMA), a side‐chain crystalline polymer, on silica were investigated. Fourier transform infrared spectroscopy and differential scanning calorimetry (DSC) measurements were made on both bulk and adsorbed PLMA. The reversible heat flow rates were observed as a function of temperature and the degree of crystallinity of the samples determined based on the broad melting transitions of the side chains in the surface samples. It was found that adsorption caused a disruption of the side‐chain crystallinity primarily in the tightly bound layer of the polymer, but did not significantly affect its glass transition temperature. A change in the packing of the hydrophobic side chains, as a result of adsorption, was also observed for the tightly adsorbed polymer. These results indicated that PLMA side chains in proximity to the silica surface have different properties from those in bulk PLMA. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 89–96 相似文献
5.
Alexander H. Soeriyadi Vanessa Trouillet Francesca Bennet Michael Bruns Michael R. Whittaker Cyrille Boyer Philip J. Barker Thomas P. Davis Christopher Barner‐Kowollik 《Journal of polymer science. Part A, Polymer chemistry》2012,50(9):1801-1811
The present study investigates the degradation behavior of various high‐molecular‐weight acrylic polymers (50,000 < Mn/g mol?1 < 100,000), namely poly(methyl methacrylate) (PMMA), poly(n‐butyl methacrylate) (PBMA), poly(n‐butyl acrylate) (PBA), and poly(lauryl methacrylate) (PLMA), under extreme environmental conditions. These polymers were synthesized via various polymerization techniques to create different end‐groups. The polymers chosen are readily applicable in the formulation of surface coatings and were degraded under conditions which replicate the harsh Australian climate, where surface coatings may reach temperatures of up to 95 °C and are exposed to broad‐spectrum UV radiation of up to 1 kW m?2. The degradation behavior of the polymeric materials on their surface was followed via ATR‐IR spectroscopy, high resolution FTIR microscopy, and X‐ray photoelectron spectroscopy. The extent of the observed thermal and photo‐oxidation is directly related to the length of the ester side group, with the degradation susceptibility decreasing in the order of PLMA > PBMA/PBA > PMMA, with PMMA still stable even after 5 months exposure to the harshest condition used (UV light at 95 °C). The general degradation mechanism involves the loss of the ester side groups to form methacrylic acid followed by cross‐linking. The effect of the variable end groups was found to be minimal. The results from this study are in good agreement with previous studies of low‐molecular‐weight model polymers under identical conditions. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
6.
《Surface and interface analysis : SIA》2005,37(1):62-70
Molecular depth profiling of polymers by secondary ion mass spectrometry (SIMS) has focused on the use of polyatomic primary ions due to their low penetration depth and high damage removal rates in some polymers. This study is the third in a series of systematic characterizations of the effect of polymer chemistry on degradation under polyatomic primary ion bombardment. In this study, time‐of‐flight SIMS (ToF‐SIMS) was used to assess 5 keV SF5+‐induced damage of ~90 nm thick spin‐cast poly(2‐hydroxyethyl methacrylate) (PHEMA) and ~130 nm thick trifluoroacetic anhydride‐derivatized PHEMA (TFAA‐PHEMA) films. The degradation of these polymers under extended SF5+ bombardment (~2 × 1014 ions cm?2) was compared to determine the effect of the pendant group chemistry on their degradation. The sputter rate and ion‐induced damage accumulation rate of PHEMA were similar to a poly(n‐alkyl methacrylate) of similar pendant group length, suggesting that the addition of a terminal hydroxyl group to the alkyl pendant group does not markedly change the stability of poly(n‐alkyl methacrylates) under SF5+ bombardment. The sputter rate and ion‐induced damage accumulation rate of TFAA‐PHEMA were much higher than a poly(n‐alkyl methacrylate) of similar pendant group length, suggesting that derivatization of the terminal hydroxyl group can significantly reduce degradation of the polymer under SF5+ bombardment. This result is in good agreement with the literature on the thermal and radiation‐induced degradation of fluorinated poly(alkyl methacrylates), which suggests that the electron‐withdrawing fluorinated pendant group increases the probability of depolymerization. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
7.
Moses T. Kabomo Frank D. Blum Suntree Kulkeratiyut Suriyaphongse Kulkeratiyut Piyawan Krisanangkura 《Journal of Polymer Science.Polymer Physics》2008,46(6):649-658
The behavior of relatively monodisperse adsorbed poly(methyl methacrylate) (PMMA) samples, from 19 to 587 kDa on silica, was studied using modulated differential scanning calorimetry and FTIR. On untreated Cab? O? Sil silica, the glass transition temperatures (Tgs) were higher (by around 30 °C), and the transitions were significantly broader (by a factor of 5–6) than those for the corresponding bulk samples. While the Tgs for the bulk polymers showed the expected dependence on molecular mass, the polymers on untreated silica showed little dependence, i.e., at the same adsorbed amounts, the glass transitions were very similar. The FTIR spectra of the adsorbed PMMA (on untreated silica) showed the presence of at least two resonances, one for the bound (hydrogen bonded to surface silanols) and another for free carbonyls. Fitting of the spectra allowed the estimation of the bound fractions of carbonyls that were dependent on the adsorbed amount, but not molecular mass. On Cab? O? Sil treated with hexamethyldisilizane (HMDS), the adsorbed PMMA exhibited glass transition behavior with little molecular‐mass dependence; the Tgs for the different PMMA samples were very similar to those of the high‐molecular mass bulk polymer, but with additional broadening of about a factor of 2. FTIR spectra for the PMMA samples on the treated silica did not show significant amounts of any of the hydrogen‐bonded carbonyl groups. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 649–658, 2008 相似文献
8.
Takeshi Mori Masafumi Hamada Toru Kobayashi Hirokazu Okamura Keiji Minagawa Seizo Masuda Masami Tanaka 《Journal of polymer science. Part A, Polymer chemistry》2005,43(20):4942-4952
The effects of structure alteration of alkyl groups and addition of ions to solutions of new thermosensitive polymer series of poly(methyl 2‐alkylamidoacrylate)s were investigated. Potential advantages of the thermosensitive polymers are their simplicity of functionalization and transition temperature control that result from their unique α,α‐disubstituited structures. Poly(methyl 2‐propionamidoacrylate) (PMPA) and poly(methyl 2‐isobutyracrylate) (PMIBA) were thermosensitive polymers, and poly(methyl 2‐acetamidoacrylate) and poly(methyl 2‐n‐butyramidoacrylate) were completely water‐soluble and ‐insoluble, respectively. The PMIBA solution showed endotherm during the phase transition, while endotherm was not detected for PMPA. The difference between the two polymers resulted from the size of the hydrophobic groups. MPA gel was prepared by copolymerization with N,N′‐methylenebis(acrylamide) and temperature‐induced volume change of the gel was continuous. The salting‐out effect of inorganic ions on PMPA solution and MPA gel followed the Hofmeister series. The inorganic (I? and SCN?) and organic ions (nPr4N+ and nBu4N+), which showed the salting‐in effect, were indicated to directly interact with PMPA chains. These ions widened the temperature range of the phase transition of the PMPA solutions. This reduced cooperativity of the phase transition was caused by size decrease of cooperative domains, which resulted from the interaction of the ions with the polymer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4942–4952, 2005 相似文献
9.
Daisuke Takeuchi Akihisa Inoue Fujio Ishimaru Kohtaro Osakada 《Journal of polymer science. Part A, Polymer chemistry》2009,47(3):959-972
The polymers with functionalized alkoxy groups and with narrow molecular weight distribution (Mw/Mn < 1.12) are obtained from the living polymerization of 2‐alkoxy‐1‐methylenecyclopropanes using π‐allylpalladium complex, [(PhC3H4)Pd(μ‐Cl)]2, as the initiator. The polymers with oligoethylene glycol groups in the alkoxy substituent are soluble in water, and hydroboration of the C?C double bond and ensuing addition of the OH groups to C?N bond of alkyl isocyanate produce the polymers with urethane pendant groups. The reaction decreases solubility of the polymer in water significantly. Di‐ and triblock copolymers of the 2‐alkoxy‐1‐methylenecyclopropanes are prepared by consecutive addition of the two or three 2‐alkoxy‐1‐methylenecyclopropane monomers to the Pd initiator. The polymers which contain both hydrophobic butoxy or tert‐butoxy group and hydrophilic oligoethylene glycol group dissolve in water and/or organic solvents, depending on the substituents. The 1H NMR spectrum of poly( 1a ‐b‐ 1h ) (? (CH2C(?CH2)CHOBu)n? (CH2C(?CH2)CH(OCH2CH2)3OMe)m? ) in D2O solution exhibits peaks because of the butoxy and ?CH2 hydrogen in decreased intensity, indicating that the polymer forms micelle particles containing the hydrophilic segments in their external parts. Aqueous solution of the polymer with a small amount of DPH (DPH = 1,6‐diphenyl‐1,3,5‐hexatriene) shows the absorbance due to DPH at concentration of the polymer higher than 5.82 × 10?5 g mL?1. Other block copolymers such as poly( 1b ‐b‐ 1h ) and poly( 1a ‐b‐ 1g ) also form the micelles that contain DPH in their core. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 959–972, 2009 相似文献
10.
Zhen Lin Zhang Lan Ying Zhang Zhi Hao Shen Guang Zhong Xing Xing He Fan Qi Feng Zhou 《Journal of polymer science. Part A, Polymer chemistry》2010,48(21):4627-4639
On the basis of the concept of mesogen‐jacketed liquid crystalline polymers, a series of new methacrylate monomers, (2,5‐bis[2‐(4′‐alkoxyphenyl) ethynyl] benzyl methacrylate (MACn, n = 4, 6, 8, 10, and 12) and 2,5‐bis[2‐(6′‐decanoxynaphthyl) ethynyl] benzyl methacrylate (MANC10), and their polymers, PMACn (n = 4, 6, 8, 10, and 12) and PMANC10 were synthesized. The bistolane mesogen with large π‐electron conjugation were side‐attached to the polymer backbone via short linkages. Various characterization techniques such as differential scanning calorimetry, wide‐angle X‐ray diffraction, and polarized light microscopy were used to study their mesomorphic phase behavior. The polymer PMACn with shorter flexible substituents (n = 4) forms the columnar nematic (?N) phase, but other polymers with longer flexible tails (n = 6, 8, 10, and 12) can develop into a smetic A (SA) phase instead of a ?N phase. The PMANC10 containing naphthyl can also form a well‐defined SA phase. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
11.
Lihong He Juan Pablo Hinestrosa Joseph M. Pickel Shanju Zhang David G. Bucknall S. Michael Kilbey II Jimmy W. Mays Kunlun Hong 《Journal of polymer science. Part A, Polymer chemistry》2011,49(2):414-422
Linear triblock terpolymers of poly(n‐butyl methacrylate)‐b‐poly(methyl methacrylate)‐b‐poly(2‐fluoroethyl methacrylate) (PnBMA‐PMMA‐P2FEMA) were synthesized by sequential reversible addition fragmentation chain transfer (RAFT) polymerization. Kinetic studies of the homopolymerization of 2FEMA by RAFT polymerization demonstrated controllable characteristics with fairly narrow polydispersities (~1.30). The resultant PnBMA‐PMMA‐P2FEMA triblock terpolymers were characterized via 1H NMR, 19F NMR, and gel permeation chromatography. These polymers formed micellar aggregates in a selective solvent mixture. The as‐formed micelles were analyzed using scanning electron microscopy and dynamic light scattering. It was found that these terpolymers could directly self‐organize into complex micelles in a tetrahydrofuran/methanol mixture with diameters that depended on polymer composition. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
12.
Studies of relationship between polymer structure and hydration environment in amphiphilic polytartaramides
下载免费PDF全文
![点击此处可从《Journal of Polymer Science.Polymer Physics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yongmei Chi Songjie Xu Xin Xu Yuting Cao Jian Dong 《Journal of Polymer Science.Polymer Physics》2017,55(2):138-145
The relationships between the chemical structures and hydration environment of the polymers can provide significant insight into the water‐amphiphilic polymer interactions. Here, the hydrophobicity of amphiphilic block copolymers poly(ethylene tartaramide‐b‐alkyl isocyanate) is gradually tuned by using of a series of pendant alkyl (isopropyl, n‐butyl, cyclopentyl, and cyclohexyl) groups. Dynamics of hydration probed by low‐field NMR relaxometry exhibits a heterogeneous environment of water molecules, corresponding to tightly bound water with slow re‐orientational mobility and loosely bound water with fast re‐orientational mobility. Progressively larger amounts of bound water are present in the copolymers, ongoing from pendant isopropyl, n‐butyl, cyclopentyl, and finally to cyclohexyl group. Water in the copolymer bearing the cyclohexyl group has a significantly high partial specific heat capacity. Therefore, hydrophobic interaction between the polymer and water is enhanced when the hydrophobicity of the polymer is increased, resulting in considerable hydrophobic hydration with decreased mobility of the bound water. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 138–145 相似文献
13.
Mahalingam Vanjinathan A. Raghavan A. Sultan Nasar 《Journal of polymer science. Part A, Polymer chemistry》2007,45(14):2959-2977
3,5‐bis(4‐aminophenoxy)phenyl phenylcarbamate—a novel AB2‐type blocked isocyanate monomer and 3,5‐bis{ethyleneoxy(4‐aminophenoxy)}phenyl carbonyl azide—a novel AB2‐type azide monomer were synthesized in high yield. Step‐growth polymerization of these monomers were found to give a first example of hyperbranched poly (aryl‐ether‐urea) and poly(aryl‐alkyl‐ether‐urea). Molecular weights (Mw) of the polymer were found to vary from 1,858 to 52,432 depending upon the monomer and experimental conditions used. The polydispersity indexes were relatively narrow due to the controlled regeneration of isocyanate functional groups for the polymerization reaction. The degree of branching (DB) was determined using 1H‐NMR spectroscopy and the values ranged from 87 to 54%. All the polymers underwent two‐stage decomposition and were stable up to 300 °C. Functionalized end‐capping of poly(aryl‐ether‐urea) using phenylchloroformate and di‐t‐butyl dicarbonate (Boc)2O changed the thermal properties and solubility of the polymers. Copolymerization of AB2‐type blocked isocyante monomer with functionally similar AB monomer were also carried out. The molecular weights of copolymers were found to be in the order of 6 × 105 with narrow dispersity. It was found that the Tg's of poly(aryl‐alkyl‐ether‐urea)s were significantly less (46–49 °C) compared to poly(aryl‐ether‐urea)s. Moreover the former showed melting transition at 154 °C, which was not observed in the latter case. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2959–2977, 2007 相似文献
14.
Peter J. Roth Daniel Kessler Rudolf Zentel Patrick Theato 《Journal of polymer science. Part A, Polymer chemistry》2009,47(12):3118-3130
Five different polymers, poly[methyl methacrylate] (PMMA), poly[lauryl methacrylate] (PLMA), poly[diethylene glycol methacrylate] (PDEGMA), poly[N‐isopropylacrylamide] (PNIPA), and poly[styrene] (PS) prepared by the RAFT process and thus terminated with dithioesters were aminolyzed in the presence of S‐3‐butynyl methane thiosulfonate (MTS), which was synthesized in two steps. Analysis of the polymers by 2D NMR, UV–vis absorbance, and gel permeation chromatography revealed them to quantitatively carry acetylene end groups connected with disulfide bridges, indicating that functional MTS reagents can be employed for end group functionalization of RAFT polymers. This versatile method is of advantage compared with conjugations with functional maleimides, where isolation of terminal thiols is often required but inexpedient for poly[(meth)acrylates] because their terminal thiols may undergo backbiting and thus avoid conjugation. The acetylene‐terminated polymers were bound to an azide functionalized glass surface in a Cu(I) catalyzed cycloaddition. The modified surfaces exhibited water contact angles corresponding to the polarity of the attached polymers. In the case of the stimulus responsive polymers PNIPA and PDEGMA, the surfaces showed temperature‐dependent contact angles. The disulfide bond connecting the polymers to the surface could be selectively cleaved and resulted in all surfaces having the same contact angle, independent of the nature of the polymer prior attached to the surface. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3118–3130, 2009 相似文献
15.
J. M. Montorns J. A. Reina J. C. Ronda 《Journal of polymer science. Part A, Polymer chemistry》2004,42(12):3002-3012
A set of poly[ω‐(4′‐cyano‐4‐biphenyloxy)alkyl‐1‐glycidylether]s were synthesized by the chemical modification of the corresponding poly(ω‐bromoalkyl‐1‐glycidylether)s with the sodium salt of 4‐cyano‐4′‐hydroxybiphenyl. New high‐molecular‐weight side‐chain liquid‐crystalline polymers were obtained with excellent yield and almost quantitative degree of modification. All side‐chain liquid‐crystalline polymers were rubbers soluble in tetrahydrofuran. The characterization by 1H and 13C NMR revealed no changes in the regioregular isotactic microstructure of the starting polymer and the absence of undesirable side reactions such as deshydrobromination. The liquid crystalline behavior was analyzed by DSC and polarized optical microscopy, and mesophase assignments were confirmed by X‐ray diffraction. Polymers that had alkyl spacers with n = 2 and 4 were nematic, those that had spacers with n = 6 and 8 were nematic cybotactic, and those that had longer spacers (n = 10 and 12) were smectic C and showed some crystallization of the side alkyl chains. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3002–3012, 2004 相似文献
16.
Bekir Dizman Mohamed O. Elasri Lon J. Mathias 《Journal of polymer science. Part A, Polymer chemistry》2006,44(20):5965-5973
New water‐soluble methacrylate polymers with pendant quaternary ammonium (QA) groups were synthesized and used as antibacterial materials. The polymers with pendant QA groups were obtained by the reaction of the alkyl halide groups of a previously synthesized functional methacrylate homopolymer with various tertiary alkyl amines containing 12‐, 14‐, or 16‐carbon alkyl chains. The structures of the functional polymer and the polymers with QA groups were confirmed with Fourier transform infrared and 1H and 13C NMR. The degree of conversion of alkyl halides to QA sites in each polymer was determined by 1H NMR to be over 90% in all cases. The number‐average molecular weight and polydispersity of the functional polymer were determined by size exclusion chromatography to be 32,500 g/mol and 2.25, respectively. All polymers were thermally stable up to 180 °C according to thermogravimetric analysis. The antibacterial activities of the polymers with pendant QA groups against Staphylococcus aureus and Escherichia coli were determined with broth‐dilution and spread‐plate methods. All the polymers showed excellent antibacterial activities in the range of 32–256 μg/mL. The antibacterial activity against S. aureus increased with an increase in the alkyl chain length for the ammonium groups, whereas the antibacterial activity against E. coli decreased with increasing alkyl chain length. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5965–5973, 2006 相似文献
17.
Aydan Dag Hakan Durmaz Gurkan Hizal Umit Tunca 《Journal of polymer science. Part A, Polymer chemistry》2008,46(1):302-313
Diels–Alder click reaction was successfully applied for the preparation of 3‐arm star polymers (A3) using furan protected maleimide end‐functionalized polymers and trianthracene functional linking agent (2) at reflux temperature of toluene for 48 h. Well‐defined furan protected maleimide end‐functionalized polymers, poly (ethylene glycol), poly(methyl methacrylate), and poly(tert‐butyl acrylate) were obtained by esterification or atom transfer radical polymerization. Obtained star polymers were characterized via NMR and GPC (refractive index and triple detector detection). Splitting of GPC traces of the resulting polymer mixture notably displayed that Diels–Alder click reaction was a versatile and a reliable route for the preparation of A3 star polymer. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 302–313, 2008 相似文献
18.
Jinqing Qu Feng Jiang Huanqin Chen Fumio Sanda Toshio Masuda 《Journal of polymer science. Part A, Polymer chemistry》2009,47(18):4749-4761
Optically active 1‐methylpropargyl esters bearing azobenzene groups, namely, (S)‐(?)‐3‐methyl‐3‐{4‐[4‐(n‐butyloxy)phenylazophenyl]carbonyl}oxy‐1‐propyne ( 1 ), (S)‐(?)‐3‐methyl‐3‐{4‐[4‐(n‐hexyloxy)phenylazophenyl]carbonyl}oxy‐1‐propyne ( 2 ), and (S)‐(?)‐3‐methyl‐3‐{4‐[4‐(n‐octyloxy)phenylazophenyl]carbonyl}oxy‐1‐propyne ( 3 ) were synthesized and polymerized with Rh+(nbd)[η6‐C6H5B?(C6H5)3] (nbd, norbornadiene) as a catalyst to afford the corresponding poly(1‐methyloropargyl ester)s with moderate molecular weights (Mn = 24,000–31,300) in good yields (79–84%). Polymers were soluble in common organic solvents including toluene, CHCl3, CH2Cl2, THF, and DMSO, whereas insoluble in diethyl ether, n‐hexane, and methanol. Large optical rotations and strong CD signals demonstrated that all the polymers take a helical structure with a predominantly one‐handed screw sense. The helical structure of the polymers changed with the addition of MeOH and heat. The trans‐azobenzene of the polymer side chains isomerized into cis on UV irradiation, which was accompanied with drastic helical conformational changes of the polymer backbone. The cis‐azobenzene moiety reisomerized into trans on visible‐light irradiation, which induced the recovery of chiral geometry of azobenzene moieties in the side chain. Conformational analysis revealed that the polymers form a tightly twisted right‐handed helical structure with a dihedral angle of 70° at the single bond of the main chain. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4749–4761, 2009 相似文献
19.
Hongyun Tai Anna Tochwin Wenxin Wang 《Journal of polymer science. Part A, Polymer chemistry》2013,51(17):3751-3761
Here we report the preparation of PEG‐based thermoresponsive hyperbranched polymers via a facile in situ reversible addition‐fragmentation chain transfer (RAFT) copolymerization using bis(thiobenzoyl) disulphide to form 2‐cyanoprop‐2‐yl dithiobenzoate in situ. This novel one‐pot in situ RAFT approach was studied firstly using methyl methacrylate (MMA) monomer, then was used to prepare thermoresponsive hyperbranched polymers by copolymerization of poly(ethylene glycol) methyl ether methacrylate (PEGMEMA, Mn = 475), poly(propylene glycol) methacrylate (PPGMA, Mn = 375) and up to 30 % of ethylene glycol dimethacrylate (EGDMA) as the branching agent. The resultant PEGMEMA‐PPGMA‐EGDMA copolymers from in situ RAFT were characterized by Gel Permeation Chromatography (GPC) and 1H‐NMR analysis. The results confirmed the copolymers with multiple methacrylate groups and hyperbranched structure as well as RAFT functional residues. These water‐soluble copolymers with tailored compositions demonstrated tuneable lower critical solution temperature (LCST) from 22 °C to 32 °C. The phase transition temperature can be further altered by post functionalization via aminolysis of RAFT agent residues in polymer chains. Moreover, it was demonstrated by rheological studies and particle size measurements that these copolymers can form either micro‐ or macro photocrosslinked gels at suitable concentrations due to the presence of multiple methacrylate groups. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3751–3761 相似文献
20.
Atsushi Kisanuki Yuji Kimpara Yoshiko Oikado Naomi Kado MITSUAKI Matsumoto Kiyoshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2010,48(22):5247-5253
Thermal polymerization of DL ‐α‐lipoic acid (LPA) in bulk without any initiator proceeded easily above the melting point of LPA. The molecular weight polymer determined by GPC was high. From the 1H NMR spectra of polymers, poly(LPA) obtained from polymerization of high purity LPA was to consist of cyclic structures, which was confirmed by ESI‐MS. Interlocked polymer consisting of poly(LPA) and dibenzo‐30‐crown‐10 entangled with each other was synthesized by the polymerization of LPA in the presence of dibenzo‐30‐crown‐10. From the DSC analysis of the polymers, glass transition temperature was estimated to be about ?11 °C, but melting point was not observed, indicating that poly(LPA) is an amorphous polymer. By photodecomposition of poly(LPA), Mn was rapidly decreased at the early stage of the decomposition. After that, the Mn of the polymer kept and then was almost constant even for a prolonged reaction time. On the basis of the results, it would be presumed that poly (LPA) obtained form polymerization of high purity LPA includes an interlocked structure. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献