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1.
C. Garrett Campbell Robson F. Storey 《Journal of polymer science. Part A, Polymer chemistry》2017,55(12):1991-1997
Lewis‐acid catalyzed degradation of poly(isobutylene‐co‐isoprene) (butyl rubber) in the presence of an alkoxybenzene compound was studied as a new route toward low molecular weight multifunctional polyisobutylenes. Simultaneous cleavage and functionalization of butyl rubber was conducted at ?70 °C and ?40 °C under TiCl4 or AlCl3 catalysis in 60/40 hexane/methylene chloride cosolvents in the presence of (3‐bromopropoxy)benzene (BPB) for various times up to 24 h. The butyl rubber (EXXON? Butyl 365) possessed M n = 1.91 × 105 g/mol, PDI = 1.66 (GPC/MALLS), and 2.30 mol % isoprene units (nearly exclusively trans ?1,4). At ?70 °C with TiCl4, molecular weight was reduced to various values within the range 7 to 11 × 103 g/mol depending on conditions; lower BPB concentration produced lower molecular weight. However, the ratio of isobutylene repeat units to BPB units (IB/Q ) remained constant at about 43:1, which is approximately the same as the ratio of isobutylene to isoprene repeat units (IB/IP) in the starting butyl rubber (42.5:1). At ?40 °C with TiCl4, molecular weight was reduced to about 5 × 103 g/mol, and IB/Q was reduced below IB/IP, indicating nearly a difunctional telechelic structure. AlCl3 was a more active catalyst and produced results similar to TiCl4 at ?40 °C, even when used at seven times lower concentration. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 1991–1997 相似文献
2.
Hiroshi Katayama Masami Kamigaito Mitsuo Sawamoto 《Journal of polymer science. Part A, Polymer chemistry》2001,39(8):1258-1267
Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry analysis revealed that the precision control (or the living nature) of the cationic polymerization of vinyl ethers with SnCl4 or TiCl4 critically depends on the Lewis acid concentration and temperature. Specifically, at an extremely low Lewis acid concentration, for example, the polymerization with the HCl–vinyl ether adduct (an initiator) is living at ?78 °C in CH2Cl2 solvent, whereas side reactions occurred at a higher concentration of SnCl4 or at a higher temperature, ?15 °C. This was more pronounced with SnCl4 than with TiCl4, which was due to a stronger Lewis acidity of SnCl4 as suggested by NMR analysis of the model reactions. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1258–1267, 2001 相似文献
3.
Da‐Wei Wan Zhou Chen Yan‐Shan Gao Qi Shen Xiu‐Li Sun Yong Tang 《Journal of polymer science. Part A, Polymer chemistry》2013,51(11):2495-2503
A series of [O?N(H)X]TiCl3 complexes derived from (arylamino)methylene phenol are prepared. The molecular structures of the complexes are characterized by 1H NMR, 13C NMR, and X‐ray analysis. Upon activation with modified methylaluminoxane (MMAO), the titanium complexes display high thermal stability and single‐site like ethylene (co)polymerization behavior at the temperatures of up to 150 °C. 1‐Octene and 1‐octadencene prove suitable to be incorporated into polyethylene backbone at 110 °C and the highest activity of 1.89 × 106 g/mol(Ti)·h·atm can be achieved. The pendant group X has great influence on the catalytic behaviors of the complexes, and PPh2 proves to be the optimal group. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2495–2503 相似文献
4.
Synthesis of Spherical Titanium Dioxide Particles by Homogeneous Precipitation in Acetone Solution 总被引:1,自引:0,他引:1
Titania powders were synthesized by thermal hydrolysis of titanium tetrachloride in a mixed solvent was studied. The dielectric constant was tuned by regulating the acetone/water volume ratio (R/H ratio) and temperature of the solvent. Hydroxypropyl cellulose (HPC) was used as a steric dispersant. The synthesis were carried out at R/H ratios of 0–4, temperatures of 70–90°C, TiCl4 concentrations of 0.05–0.2 M, HPC concentrations of 0–5 × 10–3 g/cm3, and synthesis times of 15–60 min. The TiO2 particles obtained at an R/H ratio of 0, i.e., pure water system, were fine and agglomerated. In contrast, the TiO2 particles prepared at an R/H ratio of 3 were uniform and spherical. The TiO2 particle size increased with increasing TiCl4 concentration. The synthesis temperature did not influence the particle size, but greatly influenced the morphologyof the TiO2. Adding HPC to the solution yielded more uniform and spherical particles. In addition, the synthesis time should be longer than 30 min to obtain the most uniform and spherical particles. The dielectric constant of the acetone-water mixed solvent at 28 gave the most uniform and spherical TiO2 particles. The powders prepared at the condition of 0.1 M TiCl4, R/H ratio of 3, HPC concentration of 0.001 g/cm3, temperature of 70°C, and synthesis time of 1 h exhibited the most uniform and spherical morphology. The as-synthesized powder was anatase and retained the phase below 400°C. It transformed to the rutile phase after calcination at 700°C. 相似文献
5.
Robson F. Storey Kelly A. Shoemake 《Journal of polymer science. Part A, Polymer chemistry》1999,37(11):1629-1641
Multiarm star‐branched polymers based on poly(styrene‐b‐isobutylene) (PS‐PIB) block copolymer arms were synthesized under controlled/living cationic polymerization conditions using the 2‐chloro‐2‐propylbenzene (CCl)/TiCl4/pyridine (Py) initiating system and divinylbenzene (DVB) as gel‐core‐forming comonomer. To optimize the timing of isobutylene (IB) addition to living PS⊕, the kinetics of styrene (St) polymerization at −80°C were measured in both 60 : 40 (v : v) methyl cyclohexane (MCHx) : MeCl and 60 : 40 hexane : MeCl cosolvents. For either cosolvent system, it was found that the polymerizations followed first‐order kinetics with respect to the monomer and the number of actively growing chains remained invariant. The rate of polymerization was slower in MCHx : MeCl (kapp = 2.5 × 10−3 s−1) compared with hexane : MeCl (kapp = 5.6 × 10−3 s−1) ([CCl]o = [TiCl4]/15 = 3.64 × 10−3M; [Py] = 4 × 10−3M; [St]o = 0.35M). Intermolecular alkylation reactions were observed at [St]o = 0.93M but could be suppressed by avoiding very high St conversion and by setting [St]o ≤ 0.35M. For St polymerization, kapp = 1.1 × 10−3 s−1 ([CCl]o = [TiCl4]/15 = 1.82 × 10−3M; [Py] = 4 × 10−3M; [St]o = 0.35M); this was significantly higher than that observed for IB polymerization (kapp = 3.0 × 10−4 s−1; [CCl]o = [Py] = [TiCl4]/15 = 1.86 × 10−3M; [IB]o = 1.0M). Blocking efficiencies were higher in hexane : MeCl compared with MCHx : MeCl cosolvent system. Star formation was faster with PS‐PIB arms compared with PIB homopolymer arms under similar conditions. Using [DVB] = 5.6 × 10−2M = 10 times chain end concentration, 92% of PS‐PIB arms (Mn,PS = 2600 and Mn,PIB = 13,400 g/mol) were linked within 1 h at −80°C with negligible star–star coupling. It was difficult to achieve complete linking of all the arms prior to the onset of star–star coupling. Apparently, the presence of the St block allows the PS‐PIB block copolymer arms to be incorporated into growing star polymers by an additional mechanism, namely, electrophilic aromatic substitution (EAS), which leads to increased rates of star formation and greater tendency toward star–star coupling. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1629–1641, 1999 相似文献
6.
Yu Shinke Arihiro Kanazawa Shokyoku Kanaoka Sadahito Aoshima 《Journal of polymer science. Part A, Polymer chemistry》2013,51(22):4828-4834
The living cationic polymerization of 6‐tert‐butoxy‐2‐vinylnaphthalene (tBOVN), a vinylnaphthalene derivative with an electron‐donating group, was achieved with a TiCl4/SnCl4 combined initiating system in the presence of ethyl acetate as an added base at –30 °C. The absence of side reactions at low temperature was confirmed by 1H NMR analysis of the resulting polymer. In contrast to this controlled reaction at –30 °C, reactions performed at higher temperature, such as 0 °C, frequently involved unwanted intramolecular or intermolecular Friedel–Crafts reactions of naphthalene rings due to the high electron density of these rings. The cationic polymerization of 6‐acetoxy‐2‐vinylnaphthalene, a derivative with an acetoxy group, was also controlled under similar conditions, but chain transfer reactions were not completely suppressed during the polymerization of 2‐vinylnaphthalene. The glass transition temperature (Tg) of the obtained poly(tBOVN) was 157 °C, a value higher by 94 °C than that of the corresponding styrene derivative. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4828–4834 相似文献
7.
Ethylene polymerization with long‐lifetime monopendant thienyl‐substituted group 4 metallocenes
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A series of group 4 metallocenes (RCp)[Cp―(bridge)―(2‐C4H3S)]MCl2 [M = Ti ( C1 , C2 , C3 , C4 ); M = Zr ( C5 , C6 , C7 , C8 )] bearing a pendant thiophene group on a cyclopentadienyl ring have been synthesized, characterized and tested as catalyst precursors for ethylene polymerization. The molecular structures of representative titanocenes C2 and C4 were confirmed by single‐crystal X‐ray diffraction and revealed that both complexes exist in an expected coordination environment for a monomeric bent metallocene. No intramolecular coordination between the thiophene group and the titanium center could be observed in the solid state. Upon activation by methylaluminoxane (MAO), titanocenes C1 , C2 , C3 , C4 showed moderate catalytic activities and produced high‐ or ultra‐high‐molecular‐weight polyethylene (Mv 70.5–227.1 × 104 g mol?1). Titanocene C3 is more active and long‐lived, with a lifetime of nearly 9 h at 30 °C. At elevated temperatures of 80–110 °C, zirconocenes C5 , C6 , C7 , C8 displayed high catalytic activities (up to 27.6 × 105 g PE (mol Zr)?1 h?1), giving high‐molecular‐weight polyethylene (Mv 11.2–53.7 × 104 g mol?1). Even at 80 °C, a long lifetime of at least 2 h was observed for the C8/MAO catalyst system. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
8.
M. Murat Ozmen 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(8):1215-1225
A series of strong polyelectrolyte gels were prepared in aqueous solution, using the sodium salt of 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS) as the monomer and N,N'‐methylene(bis)acrylamide (BAAm) as a crosslinker. The gels were both prepared below (?22°C) and above (25°C) the bulk freezing temperature of the water, producing cryogels and hydrogels, respectively. The crosslinker (BAAm) content was set at 17 mol%, while the initial monomer concentration Co was varied over a wide range. It was found that, at ?22°C, a macroscopic network starts to form at an initial monomer concentration of as low as 0.1 w/v%. In contrast to the conventional hydrogels formed at 25°C, the cryogels have a discontinuous morphology consisting of polyhedral pores of sizes 100–102 μm. The cryogels exhibit superfast swelling properties, as well as reversible swelling–deswelling cycles in water and acetone. An increase in the initial monomer concentration from 2.5 to 10% further increases the response rate of the cryogels due to the simultaneous increase of the porosity of the networks. 相似文献
9.
Palladium supported on silica–chitosan hybrid material (Pd‐CS@SiO2) for Suzuki–Miyaura and Mizoroki–Heck cross‐coupling reactions
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Palladium supported on silica–chitosan hybrid material was prepared and characterized using thermogravimetric and differential thermogravimetric analyses, scanning electron microscopy, and Fourier transform infrared, energy‐dispersive X‐ray and X‐ray photoelectron spectroscopies. The prepared Pd‐CS@SiO2 catalyst (1 mol%) was used for the Suzuki–Miyaura cross‐coupling reaction of various aryl halides and arylboronic acids in 95% ethanol at 80 °C and the Mizoroki–Heck reaction in dimethylformamide at 110 °C using K2CO3 as a base. The developed catalyst is well suitable for the 3R approach (recoverable, robust, recyclable) for cross‐coupling reactions without appreciable loss of its activity. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
10.
Hak Jin Kim Ji‐Hyang Lee Ju‐Yeon Lee 《Journal of polymer science. Part A, Polymer chemistry》2014,52(6):760-766
Novel X‐type polyurethane 4 containing 4‐(4‐nitrophenylazo)‐6‐nitroresorcinoxy groups as nonlinear optical (NLO) chromophores, which are parts of the polymer main chains, was prepared and characterized. Polyurethane 4 is soluble in common organic solvents such as acetone and N,N‐dimethylformamide. It shows thermal stabilities up to 270 °C from thermogravimetric analysis with glass transition temperature obtained from differential scanning calorimetry of about 134 °C. The second harmonic generation (SHG) coefficient (d33) of poled polymer film at 1064 nm fundamental wavelength is 5.37 × 10?9 esu. Polymer 4 exhibits a thermal stability up to Tg, and no significant SHG decay is observed below 135 °C, which is acceptable for NLO device applications. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 760–766 相似文献
11.
Efficient synthesis of cyclic olefin copolymers with high glass transition temperatures by ethylene copolymerization with tetracyclododecene using (tert‐BuC5H4)TiCl2(N=CtBu2)—MAO catalyst
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Wannida Apisuk Hikaru Ito Kotohiro Nomura 《Journal of polymer science. Part A, Polymer chemistry》2016,54(17):2662-2667
(tBuC5H4)TiCl2(N=CtBu2) ( 1 ) exhibited remarkable catalytic activities (12,000–43,700 kg‐polymer/mol‐Ti·h) and efficient comonomer incorporation in ethylene copolymerization with tetracyclododecene (TCD) in the presence of methylaluminoxane, and the catalytic activity by 1 increased even at 60 °C. The resultant polymers are high molecular weight amorphous poly(ethylene‐co‐TCD)s (Mn = 5.88–7.03 × 105) with uniform compositions (with high Tg values, 108–203 °C); a linear relationship between Tg values and the TCD contents was observed. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2662–2667 相似文献
12.
Jong‐Beom Baek Frank W. Harris 《Journal of polymer science. Part A, Polymer chemistry》2005,43(1):78-91
Extended self‐polymerizable poly(phenylquinoxaline) monomer mixtures {i.e.,2‐[4‐(4‐hydroxyphenoxy)phenyl]‐3‐phenyl‐6‐chloroquinoxaline and 3‐[4‐(4‐hydroxy phenoxy)phenyl]‐2‐phenyl‐6‐chloroquinoxaline, 2‐[4‐(4‐hydroxyphenoxy)phenyl]‐3‐phenyl‐6‐fluoroquinoxaline and 3‐[4‐(4‐hydroxyphenoxy)phenyl]‐2‐phenyl‐6‐fluoroquinoxaline, and 2‐(4‐fluorophenyl)‐3‐phenyl‐6‐(4‐hydroxyphenoxy)quinoxaline and 3‐(4‐fluorophenyl)‐2‐phenyl‐6‐(4‐hydroxyphenoxy)quinoxaline} more flexible and nucleophilic than a previously reported monomer mixture [i.e., 3‐(4‐hydroxyphenyl)‐2‐phenyl‐6‐fluoroquinoxaline and 2‐(4‐hydroxyphenyl)‐3‐phenyl‐6‐fluoroquinoxaline] were synthesized. The monomer mixtures were then polymerized into high‐molecular‐weight polymers. A sample was obtained, through a chlorine displacement reaction, that was a semicrystalline polymer with an intrinsic viscosity of 1.11 dL/g in m‐cresol at 30 ± 0.1 °C and two melting temperatures at 339 and 377 °C in the first differential scanning calorimetry scan. There was a melting temperature at 328 °C without a detectable glass‐transition temperature (Tg) when the sample was subjected to a second differential scanning calorimetry scan. The samples from fluorine displacement reactions were completely amorphous polymers. They had intrinsic viscosities of 0.53–0.90 dL/g in m‐cresol at 30 ± 0.1 °C and Tg's of 220–224 °C. The polymer samples from fluorine displacement reactions were evaluated with gel permeation chromatography and matrix‐assisted laser desorption/ionization time‐of‐flight analyses, which monitored the existence of certain amounts of cyclic oligomers. The thin films of the polymers had room‐temperature tensile strengths of 97–113 MPa, room‐temperature Young's moduli of 2.30–2.35 GPa, and room‐temperature elongations at break of 40–150%. The melt viscosity decreased from 107 to less than 104 Pa s at 310 °C as the frequency was increased from 10?2 to 102 rad/s. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 78–91, 2005 相似文献
13.
Tim R. Dargaville Mathew Celina Pavel M. Chaplya 《Journal of Polymer Science.Polymer Physics》2005,43(11):1310-1320
Smart materials, such as thin‐film piezoelectric polymers, are interesting for potential applications on Gossamer spacecraft. This investigation aims to predict the performance and long‐term stability of the piezoelectric properties of poly(vinylidene fluoride) (PVDF) and its copolymers under conditions simulating the low‐Earth‐orbit environment. To examine the effects of temperature on the piezoelectric properties of PVDF, poly(vinylidenefluoride‐co‐trifluoroethylene), and poly(vinylidenefluoride‐co‐hexafluoropropylene), the d33 piezoelectric coefficients were measured up to 160 °C, and the electric displacement/electric field (D–E) hysteresis loops were measured from ?80 to +110 °C. The room‐temperature d33 coefficient of PVDF homopolymer films, annealed at 50, 80, and 125 °C, dropped rapidly within a few days of thermal exposure and then remained unchanged. In contrast, the TrFE copolymer exhibited greater thermal stability than the homopolymer, with d33 remaining almost unchanged up to 125 °C. The HFP copolymer exhibited poor retention of d33 at temperatures above 80 °C. In situ D–E loop measurements from ?80 to +110 °C showed that the remanent polarization of the TrFE copolymer was more stable than that of the PVDF homopolymer. D–E hysteresis loop and d33 results were also compared with the deflection of the PVDF homopolymer and TrFE copolymer bimorphs tested over a wide temperature range. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1310‐1320, 2005 相似文献
14.
Ali Javadi Abbas Shockravi Mahmood Kamali Atefeh Rafieimanesh Ali M. Malek 《Journal of polymer science. Part A, Polymer chemistry》2013,51(16):3505-3515
A series of new organic‐soluble polyamides (PAs) bearing flexible thioether linkages and heteroaromatic thiazole units were synthesized from a novel thioether‐bridged diamine monomer (DA) and various commercially available aromatic dicarboxylic acids (1–5) via a direct polycondensation method. The resulting polymers were obtained in high yields and possessed inherent viscosities in the range of 0.41–0.80 dL g?1. All of the polymers were amorphous in nature, exhibited good solubility and could be easily dissolved in amide‐type polar aprotic solvents and even dissolved in less polar solvents (e.g., tetrahydrofuran, pyridine, and acetone). They showed excellent thermal stability with glass transition temperatures between 207 and 239 °C and 10% weight loss temperatures in excess of 424 °C in nitrogen and 469 °C in air atmosphere. The optical transmittances of the PA films at 450 nm were higher than 85% for the thickness of ~10 μm. The combination of the thiazole moieties and flexible thioether linkages provided PAs with high average refractive indices (nav) of 1.7414–1.7542 and low birefringences (Δn) of 0.0061–0.0087 at 632.8 nm. In particular, the nav of PA‐5 derived from DA and 2,2′‐dithiodibenzoic acid exhibited the highest refractive index (1.7542) in the high refractive index PAs. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3505–3515 相似文献
15.
Paul Dervan Fawaz Aldabbagh Per B. Zetterlund Bunichiro Yamada 《Journal of polymer science. Part A, Polymer chemistry》2003,41(2):327-334
Styrene radical polymerizations mediated by the imidazolidinone nitroxides 2,5‐bis(spirocyclohexyl)‐3‐methylimidazolidin‐4‐one‐1‐oxyl (NO88Me) and 2,5‐bis(spirocyclohexyl)‐3‐benzylimidazolidin‐4‐one‐1‐oxyl (NO88Bn) were investigated. Polymeric alkoxyamine (PS‐NO88Bn)‐initiated systems exhibited controlled/living characteristics at 100–120 °C but not at 80 °C. All systems exhibited rates of polymerization similar to those of thermal polymerization, with the exception of the PS‐NO88Bn system at 80 °C, which polymerized twice as quickly. The dissociation rate constants (kd) for the PS‐NO88Me and PS‐NO88Bn coupling products were determined by electron spin resonance at 50–100 °C. The equilibrium constants were estimated to be 9.01 × 10?11 and 6.47 × 10?11 mol L?1 at 120 °C for NO88Me and NO88Bn, respectively, resulting in the combination rate constants (kc) 2.77 × 106 (NO88Me) and 2.07 × 106 L mol?1 s?1 (NO88Bn). The similar polymerization results and kinetic parameters for NO88Me and NO88Bn indicated the absence of any 3‐N‐transannular effect by the benzyl substituent relative to the methyl substituent. The values of kd and kc were 4–8 and 25–33 times lower, respectively, than the reported values for PS‐TEMPO at 120 °C, indicating that the 2,5‐spirodicyclohexyl rings have a more profound effect on the combination reaction rather than the dissociation reaction. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 327–334, 2003 相似文献
16.
Dr. Mareike Liebertseder Dr. Carina B. Maliakkal Marlene Crone Dr. Gülperi Nails Dr. Maria Casapu Prof. Dr. Jan-Dierk Grunwaldt Prof. Dr. Michael Türk Prof. Dr. Christian Kübel Prof. Dr. Claus Feldmann 《ChemCatChem》2024,16(2):e202301358
TiO2−CeO2−Pt hollow nanospheres (1 wt-% Pt) are realized using a liquid-phase strategy using NaCl as a template. The NaCl template is first coated with TiO2 and thereafter with CeO2 via the hydrolyzation of TiCl(OiPr)3 and Ce(OiPr)4 as suitable alkoxides. Finally, the NaCl template is removed by washing with water. The resulting @TiO2−CeO2 hollow nanospheres (□: inner cavity) exhibit an outer diameter of 140–180 nm, a wall thickness of 30–40 nm, an inner cavity of 80–100 nm, a specific surface area of 210 m2/g, a pore volume and area of 0.08 cm3/g and 191 m2/g, mainly with micropores ≥5 Å and ≤14 Å. The hollow nanosphere support is impregnated with Pt nanoparticles, using two different methods – a wet-chemical deposition (Pt(ac)2, acetone, 25 °C) and a supercritical fluid reactive deposition (SFRD) process ([Pt(COD)Me2], supercritical CO2, 80 °C, 15.6 MPa) resulting in an uniform size distribution with Pt nanoparticles 2.5±0.1 nm (TiO2−CeO2−PtWCD) and 2.3±0.1 nm (TiO2−CeO2−PtSFRD) in size. The catalytic properties of the TiO2−CeO2−Pt hollow nanospheres are evaluated for CO oxidation between 50 and 500 °C. A promising catalytic activity and stable light-out/light-off temperatures are observed especially for the TiO2−CeO2−PtSFRD sample, indicating the suitability of hollow nanospheres as high-porosity catalyst material. 相似文献
17.
Vinyl phenylboronic acid controlling co‐monomer for nitroxide mediated synthesis of thermoresponsive poly(2‐N morpholinoethyl methacrylate)
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Xeniya Savelyeva David Chondon Milan Marić 《Journal of polymer science. Part A, Polymer chemistry》2016,54(11):1560-1572
Low concentrations of 4‐vinylphenylboronic acid (VPBA) were copolymerized with 2‐N‐morpholinoethyl methacrylate (MEMA) by nitroxide mediated polymerization using BlocBuilder? unimolecular initiator at 80 to 90 °C. The MEMA/VPBA copolymerizations were performed at initial feed compositions (fVPBA,0) of 0.05 to 0.10 VPBA, with fVPBA,0 = 0.10 using dimethylacetamide (DMAc) solvent being most effective, as seen by a linear increase in number average molecular weight, Mn, versus conversion and low dispersity, ? < 1.40. The copolymers were further chain‐extended with a second batch of VPBA, resulting in a block copolymer with monomodal molecular weight distribution and ? = 1.66. For MEMA/VPBA copolymers, increases in VPBA composition and polymer solution concentration resulted in decreases in the cloud point temperature (CPT, typically varied between 27.4–37.8 °C) and CPT increased from 31.2 to 33.8 °C to about 88 °C with decreases in pH from 7 to 4. Rheological tests with small angle light scattering (SALS) confirmed CPTs measured by UV‐Vis and DLS. These copolymers were targeted as models to combine possible glucose‐sensing boronic acid functionality the thermoresponsiveness provided by MEMA groups. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1560–1572 相似文献
18.
Sukhdeep Kaur Gurmeet Singh Virendra K. Gupta 《Journal of polymer science. Part A, Polymer chemistry》2008,46(22):7299-7309
Ethylene polymerizations were performed using catalyst based on titanium tetrachloride (TiCl4) supported on synthesized poly(methyl acrylate‐co‐1‐octene) (PMO). Three catalysts were synthesized by varying TiCl4/PMO weight ratio in chlorobenzene resulting in incorporation of titanium in different percentage as determined by UV‐vis spectroscopy. The coordination of titanium with the copolymer matrix was confirmed by FTIR studies. The catalysts morphology as observed by SEM was found to be round shaped with even distributions of titanium and chlorine on the surface of catalyst. Their performance was evaluated for atmospheric polymerization of ethylene in n‐hexane using triethylaluminum as cocatalyst. Catalyst with titanium incorporation corresponding to 2.8 wt % showed maximum activity. Polyethylenes obtained were characterized for melting temperature, molecular weight, morphology and microstructure. The polymeric support utilized for TiCl4 was synthesized using activators regenerated by electron transfer (ARGET) Atom Transfer Radical Polymerization (ATRP) of methyl acrylate (MA) and 1‐octene (Oct) with Cu(0)/CuBr2/tris(2‐(dimethylamino)ethyl)amine (Me6TREN) as catalyst and ethyl 2‐bromoisobutyrate (EBriB) as initiator at 80 °C. The copolymer poly(methyl acrylate‐1‐octene; PMO) obtained showed monomodal curve in Gel Permeation Chromatography (GPC) with polydispersity of 1.37 and copolymer composition (1H NMR; FMA) of 0.75. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7299–7309, 2008 相似文献
19.
Tetsushi Kijima Masakazu Nishida Haruhiko Fukaya Masato Yoshida Hideo Sawada 《Journal of polymer science. Part A, Polymer chemistry》2013,51(12):2555-2564
A reddish‐brown fluoroalkyl end‐capped 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS) oligomer/acetone composite was prepared by heating the white oligomer powder with acetone at 80 °C for 3 h. The color was not observed in the corresponding non‐fluorinated AMPS oligomer/acetone composite, which was prepared under similar conditions. The coloring was probably caused by the formation of acetone polyaldol condensation products in the fluorinated oligomeric gel network cores. The colored RF‐(AMPS)n‐RF/acetone composite powders were stable and did not exhibit any color change after 2 years in natural light at room temperature. The colored composite powders dissolved in methanol to give a reddish‐brown solution at room temperature. However, the retro‐polyaldol condensation decolored the solution after 1 day at room temperature. This is the first example of the retro‐aldol polycondensation of acetone under mild conditions. The decoloration increased by between 38‐ and 70‐fold under UV irradiation, compared with that in dark conditions. The coloring–decoloring behavior was consistent and repeatable; therefore our fluorinated oligomer/acetone composites are promising candidates for new fluorinated coloring materials. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2555–2564 相似文献
20.
Lele Zhao Shouxin Wang Yuanyang Wang Zhihong Li 《Surface and interface analysis : SIA》2017,49(3):173-176
Titanium dioxide (TiO2) aerogels were prepared with sol–gel ambient pressure drying method by using titanium tetrachloride (TiCl4) as precursor and tetraethoxysilane as modifier, calcinated at different temperature and characterized by X‐ray diffraction, transmission electron microscopy and small angle X‐ray scattering. The results showed that the TiO2 aerogels remained amorphous under 500 °C, changed to anatase from 600 °C and further changed to rutile from 900 °C. Between 60 °C and 500 °C, the primary particles within the samples concentrated mainly upon small sizes, enlarged and diverged remarkably above 600 °C. The crystalline grains grew and agglomerated with the rise of the calcination temperature. The TiO2 aerogels at a temperature higher than 800 °C have better stability than anatase because of the formation of partial Ti―O―Si bonds. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献