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Micromechanical properties of poly(n-isopropylacrylamide)hydrogel microspheres determined using a simple method

Particuology 2015年第2期13卷 164-172页

作者： Mei Yuan Xiaojie Ju Rui Xie Wei Wang Liangyin Chu School of Chemical Engineering Sichuan University

Temperature-responsive poly（n-isopropylacrylamide）（PnIPAM） hydrogel microspheres have attracted extensive attention because of their promising diverse biomedical applications. A quantitative understanding of the micromechanical properties of these microspheres is essential for their practical application. Here, we report a simple method for the characterization of the elastic properties of PnIPAM hydrogel microspheres. The results show that PnIPAM hydrogel microspheres exhibit elastic deformation and the obtained force-deformation experimental data fits the Hertz theory well. The moduli of elasticity of the PnIPAM hydrogel microspheres prepared under different conditions were systematically investigated in this work for the first time. The Pn1PAM hydrogel microsphere composition significantly affects their micromechanical properties and their temperature sensitivity behavior. PnIPAM hydrogel microspheres with a larger equilibrium volume change have a lower modulus of elasticity. The modulus of elasticity of the PnIPAM hydrogel microspheres at body temperature （37 ℃, above the lower critical solution temperature （LCST） of PnIPAM） is much higher than that at room temperature （25 ℃, below the LCST of PnIPAM） because ofthermo-induced volume shrinkage and an increase in stiffness. These results provide valuable guidance for the design of smart materials for practical biomedical applications. Moreover, the simple microcompression method presented here also provides a versatile way to investigate the micromechanical properties of microscopic biomedical materials.

关键词： poly（n-isopropylacrylamide） Microspheres Micromechanical properties Modulus of elasticity Temperature-responsive volume change Lower critical solution temperature

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Enhanced Stability of Anisotropic Gold nanoparticles by poly(n-isopropylacrylamide)

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Journal of Materials Science & Technology 2014年第5期30卷 441-448页

作者： Jiayun Hu Chase A.Brackemyer Hongsik Byun Jun-Hyun Kim Department of Chemistry Illinois State UniversityNormalIL 61790-4160USA Department of Chemical System Engineering Keimyung UniversityDaegu 704-701South Korea

A simple synthetic method has been described to prepare anisotropic gold nanoparticles （AunPs） possessing unique optical and structural properties at room temperature, and subsequently the nanoparticles have been stabilized by temperature-sensitive poly（n-isopropylacrylamide）, or poly（nIPAM）. Although poly（nIPAM） does not exhibit a strong binding affinity to gold, simply introducing poly（nIPAM） to these unstable anisotropic AunPs can maintain the original structures and absorption properties for several weeks. This increased stability is presumably caused by the adsorbed polymer layer around the anisotropic AunPs. The existence of adsorbed linear poly（nIPAM） around the AunPs is confirmed through the reversible absorption properties of the nanoparticles upon heating and cooling. To verify the presence of weak attractive forces （e.g., van der Waals, dipole-dipole, and possible hydrogen bonding） between the polymer and the AunPs, various concentrations of linear poly（nIPAM） are introduced during the formation of the AunPs resulting in the systematical control of the size and roughness of the nanoparticles. In addition, the preferential attachment of pre-formed anisotropic AunPs on cross-linked poly（nIPAM） nanoparticles indicates the presence of weak attractive forces between AunPs and poly（nIPAM）. As such, poly（nIPAM） and its derivatives can serve as a useful stabilizing and capping agent to preserve the properties of the anisotropic AunPs.

关键词： Anisotropic gold nanoparticles poly（n-isopropylacrylamide） Stability polymer nanoparticles

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Microwave-assisted Preparation of Temperature Sensitive poly(n-isopropylacrylamide) Hydrogel with Improved Responsive Properties

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Chinese Chemical Letters 2006年第3期17卷 361-364页

作者： Shao Hua SHI Li Jian LIU Department of polymer Science College of Chemistry and Molecular Science Wuhan University Key Laboratory of Biomedical Polymers （Wuhan University） Ministry of Education Wuhan 430072 R ＆ D Center Nhwa Pharmaceutical Group Xuzhou 221007

poly（n-isopropylacrylamide）-based hydrogel was prepared under microwave irradiation The hydrogel thus prepared, comparing with that prepared by thermal heating method, exhibits faster swelling and shrinking kinetics. The improved responsive properties are due to the more heterogeneous and porous networks formed under microwave irradiation.

关键词： Microwave poly（n-isopropylacrylamide） hydrogel fast response.

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Y-shaped block copolymers of poly(ethylene glycol) and poly(n-isopropylacrylamide) synthesized by ATRP

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Chinese Chemical Letters 2009年第11期20卷 1353-1356页

作者： Xin De Tang Xiao Chao Liang nian Feng Han Institute of new Materials Shandong Jiaotong University Ji'nan 250023 China College of Chemistry & Molecular Engineering Peking University Beijing 100871 China

novel Y-shaped block copolymers of poly（ethylene glycol） and poly（n-isopropylacrylamide）, PEG-b-（PnIPAM）2, were successfully synthesized through atom transfer radical polymerization （ATRP）. A difunctional macroinitiator was prepared by esterification of 2,2-dichloroacetyl chloride with poly（ethylene glycol） monomethyl ether （PEG）. The copolymers were obtained via the ATRP ofn-isopropylacrylamide （nIPAM） at 30℃ with CuCl/Me6TREn as a catalyst system and DMF/H2O （v/v = 3：1） mixture as solvent. The resulting copolymers were characterized by gel permeation chromatography （GPC） and ^1H nMR. These block copolymers show controllable molecular weights and narrow molecular weight distributions （PDI 〈 1.15）. Their phase transition temperatures and the corresponding enthalpy changes in aqueous solution were measured by differential scanning calorimetry （DSC）. As a result, the phase transition temperature of PEG45-b-（PnIPAM55）2 is higher than that of PnIPAM, however, the corresponding enthalpy change is much lower, indicating the significant influence of the macromolecular composition and architecture on the phase transition.

关键词： Y-shaped Block copolymer poly（ethylene glycol） poly（n-isopropylacrylamide） Atom transfer radical polymerization （ATRP）

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Laterally Sandwich-typed Hydrogel Columns with Liner poly(n-isopropylacrylamide) Layer:Preparation, Swelling/deswelling Kinetics and Drug Delivery Characteristics

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Journal of Wuhan University of Technology(Materials Science) 2012年第1期27卷 115-119页

作者：李莹肖新才 School of Pharmacy South-Central University for NationalitiesWuhan 430074China

A novel thermo-responsive hydrogel column, featured with both ends of linear poly（n- isopropylacrylarnide）（PnIPAM） chains being grafted onto cross-linked PnIPAM chains, was reported. The laterally sandwich-typed hydrogel columns were fabricated by radical polymerization in a three-step process using a method of ice-melting synthesis. The initiating path, morphology and thermoresponsive characteristics of the prepared hydrogel columns were experimentally studied. The results show that the hydrogel column obtained by the initiator inside part has more quick swelling and deswelling rates responsing to temperature cycling than other hydrogels owing to linear PnIPAM chains to form supermacroporous structure. The proposed hydrogel structure provide a new mode of the phase transition behavior for thermo-sensitive ＂smart＂ or ＂intelligent＂ monodisperse micro-actuators, which is highly attractive for targeting drug delivery systems, chemical separations, and sensors and so on.

关键词： ice-melting synthesis laterally sandwich-typed hydrogel columns swelling/de-swellingrates poly（n-isopropylacrylamide）

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Temperature-pH Sensitive IPn Hydrogels Composed of Silk Sericin and poly(n-isopropylacrylamide)

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Chinese Chemical Letters 2006年第3期17卷 403-406页

作者： Wen WU Wen Jing LI Li Qun WAnG Ke Hua TU Wei Lin SUn Deparment of polymer Science and Engineering Zhejiang University Hangzhou 310027 ningbo Institute of Technology Zhejiang University Ningbo 315100

Interpenetrating polymer network （IPn） composed of silk sericin （SS） and poly（n-isopropylacrylamide）（PnIPAAm） was prepared. The morphology of the IPns, in which the SS phase was stained with ammonium cuprate, was examined with TEM and a relative homogeneous distribution of the two polymers was exhibited. The swelling behavior of the IPn hydrogels showed both temperature and pH dependences.

关键词： Silk sericin poly（n-isopropylacrylamide） interpenetrating polymer network.

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nMR study on the effects of sodium n-dodecyl sulfate on coil-to-globule transition of poly（n-isopropylacrylamide） in aqueous solutions

NMR study on the effects of sodium n-dodecyl sulfate on coil...

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2011年全国高分子学术论文报告会

作者： Jianqiang Chen a,Xiaoliang Gong b,Hu Yang a,Yefeng Yao b,Min Xu b,Qun Chen b,Rongshi Cheng a,c (a.Key Laboratory of Mesoscopic Chemistry of MOE,Department of polymer Science and Technology,School of Chemistry and Chemical Engineering,nanjing University,nanjing 210093,P.R.China) (b.Physics Department and Shanghai Key Laboratory of Magnetic Resonance,East China normal University,Shanghai 200062,P.R.China) (c.College of Material Science and Engineering,polymer Institute,South China University of Technology,Guangzhou,Guangdong 510640,P.R.China)

＜正＞The effects of sodium n-dodecyl sulfate （SDS） on the conformational changes of thermosensitive poly（n-isopropylacrylamide）（PnIPAM） in dilute aqueous solutions are investigated by the

关键词： poly（n-isopropylacrylamide） sodium n-dodecyl sulfate coil-to-globule transition nMR techniques

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THERMAL-SEnSITIVE BETA-CYCLODEXTRIn-COnTAInInG poly(nisopropylacrylamide)HYDROGELS CROSSLInKED BY Si—O—Si BOnDS—SYnTHESIS,CHARACTERIZATIOn AnD PROLOnGInG In VITRO RELEASE OF 5-FLUOROURACIL

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Chinese Journal of polymer Science 2005年第5期23卷 513-519页

作者： Jian-tao Zhang Shi-wen Huang Ya-nan Xue Ji Liu and Ren-xi Zhuo Key Laboratory of Biomedical polymers,Ministry of Education Department of Chemistry,Wuhan University,Wuhan 430072,China Key Laboratory of Biomedical polymers Ministry of Education Department of Chemistry Wuhan University Wuhan 430072 China

A series of novel p（n-isopropylacrylamide）（PnIPAM） hydrogels were synthesized by radical copolymerization of n-isopropylacrylamide （nIPAM） and 3-methacryloxypropyltrimethoxysilane （MPTMS）. The copolymers were then crosslinked through hydrolysis of the siloxane in acetic acid/water mixed solvent. Beta-cyclodextrin （Beta-CD） was introduced into the polymeric networks by condensation of 3-glycidoxypropyltrimethoxysilane derived beta-cyclodextrin （KH560-beta-CD） with MPTMS under acidic condition. These gels were heterogeneous, porous and exhibited fast deswelling kinetics when the temperature was elevated to above lower critical solution temperature （LCST）. The swelling ratios of the gels containing beta-CD at room temperature were higher than that of the normal PnIPAM hydrogel, which was caused by the lower crosslinking density in beta-CD contained gels. In comparison to that of the normal PnIPAM gel, the amount of loaded-drug in the hydrogel containing beta-CD was higher, and the release time of 5-fluorouracil （5-Fu） was prolonged, which was attributed to the formation of inclusion compounds between 5-Fu and beta-CD in gel network.

关键词： Hydrogel Thermal-sensitive poly（n-isopropylacrylamide） Beta-Cyclodextrin Fast responsive.

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HYDRATIOn AnD PHASE SEPARATIOn OF TEMPERATURE-SEnSITIVE WATER-SOLUBLE polyMERS

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Chinese Journal of polymer Science 2011年第1期29卷 13-21页

作者： Fumihiko Tanaka Tsuyoshi Koga Hiroyuki Kojima Francoise M.Winnik Department of polymer Chemistry Graduate School of EngineeringKyoto University Department of Chemistry and Faculty of Pharmacy University of Montréal

Collapse of a poly（n-isopropylacrylamide）（PnIPAM） chain upon heating and phase diagrams of aqueous PnIPAM solutions with very fiat LCST phase separation line are theoretically studied on the basis of cooperative dehydration （simultaneous dissociation of bound water molecules in a group of correlated sequence）, and compared with the experimental observation of temperature-induced coil-globule transition by light scattering methods. The transition becomes sharper with the cooperativity parameter σ of hydration. Reentrant coil-globule-coil transition in mixed solvent of water and methanol is also studied from the viewpoint of competitive hydrogen bonds between polymer-water and polymer-methanol. The downward shift of the cloud-point curves （LCST cononsolvency） with the mole fraction of methanol due to the competition is calculated and compared with the experimental data. Aqueous solutions of hydophobically-modified PnIPAM carrying short alkyl chains at both chain ends （telechelic PnIPAM） are theoretically and experimentally studied. The LCST of these solutions is found to shift downward along the sol-gel transition curve as a result of end-chain association （association-induced phase separation）, and separate from the coil-globule transition line. Associated structures in the solution, such as flower micelles, mesoglobules and higher fractal assembly, are studied by USAnS with theoretical modeling of the scattering function.

关键词： Cooperative dehydration LCST phase separation poly（n-isopropylacrylamide） Cononsolvency Coil-globule transition Flower micelle.

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Slightly Cross-Linked polyrotaxanes Made by Linking α-Cyclodextrins Entrapped in polyrotaxanes Using Hexamethylene Diisocyanate

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Chinese Journal of Chemistry 2012年第10期30卷 2453-2460页

作者：李硕王锦姜岚叶霖张爱英冯增国 School of Materials Science and Engineering Beijing Institute of TechnologyBeijing 100081China

In this study polyrotaxane （PR）-based triblock copolymers were first synthesized via the atom transfer radical polymerization （ATRP） of n-isopropylacrylamide initiated with the self-assembly of a distal 2-bromoisobutyryl end-capped Pluronie 17R4 with a varying amount of a-cyclodextrins （a-CDs） in the presence of CuCI/PMDETA at 25 ℃ in aqueous solution. The a-CDs entrapped on the copolymer chain were then linked with hexamethylene diisocyanate to give rise to novel slightly cross-linked polyrotaxanes （SCPRs） in DMF at 45 ℃. The structures of the PR-based triblock copolymers and SCPRs were characterized by 1H nMR, 13C CP/MAS, GPC and TGA analy- ses. The number-average molecular weight of the resulting SCPRs was nearly three and five times of their precursor after linking with a low polydispersity index range of 1.08--1.28. The thermo-responsive transition of both PR-based supramolecular polymers in aqueous solution was demonstrated by turbidity measurements and the self-aggregated morphologies were also evidenced by TEM observations.

关键词： α-cyclodextrin polyrotaxane ATRP poly（n-isopropylacrylamide） hexamethylene diisocyanate

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