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111.
Anna Miasnikova André Laschewsky 《Journal of polymer science. Part A, Polymer chemistry》2012,50(16):3313-3323
The easily accessible, but virtually overlooked monomer methoxy diethylene glycol acrylate was polymerized by the RAFT method using monofunctional, difunctional, and trifunctional trithiocarbonates to afford thermoresponsive polymers exhibiting lower critical solution temperature‐type phase transitions in aqueous solution. The use of the appropriate RAFT agent allowed for the preparation and systematic variation of polymers with defined molar mass, end‐groups, and architecture, including amphiphilic diblock, symmetrical triblock, and triarm star‐block copolymers, containing polystyrene as permanently hydrophobic constituent. The cloud points (CPs) of the various polymers proved to be sensitive to all varied parameters, namely molar mass, nature, and number of the end‐groups, and the architecture, up to relatively high molar masses. Thus, CPs of the polymers can be adjusted within the physiological interesting range of 20–40 °C. Remarkably, CPs increased with the molar mass, even when hydrophilic end groups were attached to the polymers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
112.
Methanol‐induced change of the mechanism of the temperature‐ and pressure‐induced collapse of N‐Substituted acrylamide copolymers 下载免费PDF全文
Christian H. Hofmann Sebastian Grobelny Paweł T. Panek Laura K. M. Heinen Ann‐Kristin Wiegand Felix A. Plamper Christoph R. Jacob Roland Winter Walter Richtering 《Journal of Polymer Science.Polymer Physics》2015,53(7):532-544
The solvation of two differently composed linear statistical copolymers from N,N‐diethyl acrylamide (DEAm) and N‐isopropyl acrylamide is studied by Fourier‐transform infrared spectroscopy. The solvent is changed from pure water to mixtures with methanol to investigate the cononsolvency effect. Furthermore, the influence of temperature and pressure is studied. The IR results are interpreted by sub‐band fitting of the amide I' band and quantum–chemical calculations. There are significant differences between the two copolymers that cannot be explained by a weighted superposition of the homopolymer spectra. An excess of DEAm units leads to a high number of nonsolvated side chains already in pure water. This high number is reached for equimolar copolymers only when methanol is added. The mechanism of the temperature‐ or pressure‐induced phase transition changes upon methanol addition for both copolymers. Generally, the phenomena are deduced to cooperativity at equimolar composition that is perturbed by methanol. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 532–544 相似文献
113.
《Macromolecular rapid communications》2017,38(6)
Poly(N‐isopropylacrylamide‐co‐3‐(trimethoxysilyl)propyl methacrylate), P(NIPAAm‐co‐TMSPMA), copolymers with relatively high TMSPMA contents without insoluble fraction are successfully synthesized. Subsequent sol–gel reactions in both the absence and presence of tetraethyl orthosilicate lead to gels with high gel fractions. The resulting gels undergo gel collapse at 28.6–28.7 °C, i.e., below that of poly(N‐isopropylacrylamide) homopolymer of 34.3 °C. Unexpectedly, the theophylline‐loaded hybrid gels release the drug not only below but also above the gel collapse temperature (GCT) with considerable rates and released amounts of drug. Surprisingly, evaluation of the sustained release profiles by the Korsmeyer–Peppas equation indicates that the release occurs by Fickian diffusion above GCT, which can be attributed to the lack of significant drug–polymer interaction at such temperatures. These results can be widely applied for the design and utilization of TMSPMA‐based sol–gel polymer hybrids with desired release profiles of solutes below and above GCT for a variety of applications.
114.
Dominik Segiet Robert Jerusalem Frank Katzenberg Joerg C. Tiller 《Journal of polymer science. Part A, Polymer chemistry》2020,58(5):747-755
Thermoresponsive hydrogels are of great importance as smart materials. They are usually composed of cross-linked polymers with a lower critical solution temperature (LCST). Although much is known about networks of poly(N-isopropylacrylamide), all other polymers are somewhat neglected. In this work, the temperature-dependent swelling behavior of differently cross-linked thermoresponsive poly(2-ethyl-2-oxazoline) (PEtOx) hydrogels were investigated with regard to varying parameters of the network composition. It was found that the degrees of swelling of the hydrogels converge for a certain polymer/solvent system at a distinct temperature independent of its degree of cross-linking. Furthermore, this temperature correlates with the LCST of the respective starting PEtOx. Its net chain molecular weight Mc only affects the maximum degree of swelling and thus, the swelling–deswelling rate of the hydrogel. The fundamental structure/property relations found in this study could be useful to predict the behavior of other thermoresponsive hydrogels. 相似文献
115.
Atsushi Nagai Kenta Kokado Junpei Miyake Yoshiki Cyujo 《Journal of polymer science. Part A, Polymer chemistry》2010,48(3):627-634
Novel water‐soluble copolymers containing 4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BODIPY) dyes were synthesized by reversible addition‐fragmentation chain transfer (RAFT) polymerization. The copolymers with both number‐average molecular weight between 5.0 × 103 and 5.8 × 103 and narrow molecular weight distribution (Mw/Mn < 1.19) were obtained by the copolymerization of (2‐dimethylamino)ethyl methacrylate (DMAEMA) and BODIPY‐based methyl methacrylate ( 1 ) with 2,2′‐azobis(isobutyronitrile) (AIBN) as an initiator in the presence of cumyl dithiobenzoate (CDB) as a chain transfer agent (CTA). The structures of the resulting copolymers were characterized by 1H, 13C, and 11B NMR spectroscopies, and the comonomer compositions were good consistent with the feed ratio. Characteristic optical properties of the obtained copolymers were investigated by UV‐vis and PL spectroscopic methods. The copolymers composed of [DMAEMA]: [1] = 98.0:2.0 and 99.4:1.4 led to thermoresponsive polymers having phase separation temperatures at 32 °C and 40 °C, respectively, depending on the compositions of hydrophilic/hydrophobic balances. Further, the effective reversible decrease/increase of the emission intensity of the copolymers led to the reversible formation/inhibition of the H‐aggregation between two BODIPY planes in the copolymers on heating and cooling across the border of LCST. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 627–634, 2010 相似文献
116.
Siti Sarah Abdul Rahman Daisuke Kawaguchi Daisaku Ito Atsushi Takano Yushu Matsushita 《Journal of Polymer Science.Polymer Physics》2009,47(22):2272-2280
The phase behavior of statistical copolymers composed of (4‐tert‐butylstyrene) (B) and (4‐tert‐butoxystyrene) (O), abbreviated as s‐BO, with polyisoprene (I) was investigated by optical microscopic (OM) observation and small‐angle neutron scattering (SANS) measurements. It has been known that B/I blend shows lower critical solution temperature (LCST) type phase diagram, while O/I blend has upper critical solution temperature (UCST) type one. Several blends of s‐BOs having mol fraction of B, mB, comparable to 0.50, with I showed both UCST and LCST type phase diagram. Furthermore, UCST type phase behavior was observed for blends having small mB, while LCST type one was for that of large mB at all used temperatures. Hence, the phase behavior of s‐BO/I blend can be understood as a result of the competition of two interactions having opposite temperature dependence. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2272–2280, 2009 相似文献
117.
118.
Mikko Karesoja Jason McKee Erno Karjalainen Sami Hietala Lotta Bergman Mika Linden Heikki Tenhu 《Journal of polymer science. Part A, Polymer chemistry》2013,51(23):5012-5020
Mesoporous silica particles were grafted with thermoresponsive poly(ethyleneoxide‐b‐N‐vinylcaprolactam), PEO‐b‐PVCL. N‐vinylcaprolactam was first polymerized on particle surfaces using surface initiated atom transfer radical polymerization (SI‐ATRP) and then, the poly(ethyleneoxide) blocks were attached to the PVCL chain ends with click chemistry. The sizes, thermoresponsiviness, and colloidal stability of SiO2‐PVCL and SiO2‐PVCL‐b‐PEO particles and their aqueous dispersions were studied by scanning electron microscopy, turbidimetry, dynamic light scattering, zeta sizer, and microcalorimetry. The phase separation temperature of the PEO‐b‐PVCL grafted particles did not considerably differ from that of the SiO2‐PVCL particles. The zeta potential of the grafted particles was close to zero at room temperature but decreased strongly upon heating. The decrease is related to the collapse of the PVCL blocks and correspondingly, the exposure of the silica surface toward the aqueous phase. The colloidal stability of the particles could be enhanced by adding PEO blocks to the chain ends of the PVCL grafts. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5012–5020 相似文献
119.
The preparation of a novel peptide/dendrimer hybrid is reported in which an elastin‐like oligopeptide is successfully assembled onto a poly(amidoamine) dendrimer surface (G4‐ELP), and its unique thermo‐responsive behavior is discussed. As a result, the G4‐ELP is found to exhibit LCST behavior in the pH range 3–10 including physiological temperature range under neutral‐pH conditions. Moreover, cooperative interplay between the folding state of the ELP shell and the ionization state of the dendrimer core enables the G4‐ELP to control its LCST widely by pH variation. This achievement provides a new insight for the design of dual‐responsive materials with a potential in biological applications.
120.
Nicky Chan So Young An Nathan Yee Jung Kwon Oh 《Macromolecular rapid communications》2014,35(7):752-757
The synthesis, tunable thermoresponsive properties, and self‐assembly of dual redox and thermoresponsive double hydrophilic block copolymers having pendant disulfide linkages (DHBCss) are reported. Well‐defined DHBCss composed of a hydrophilic poly(ethylene oxide) block and a dual thermo‐ and reduction‐responsive random copolymer block containing pendant disulfide linkages are synthesized by atom transfer radical polymerization. Their lower critical solution temperature (LCST) transitions are adjusted through modulating pendant hydrophobic–hydrophilic balance with disulfide–thiol–sulfide chemistry. Further, these DHBCss derivatives are converted to disulfide‐crosslinked nanogels at temperatures above LCST through temperature‐driven self‐assembly and in situ disulfide crosslinking. They exhibit enhanced colloidal stability and further reduction‐responsive degradability, thus demonstrating versatility of dual thermo‐ and reduction‐responsive smart materials.