Thermoresponsive copolymers: from fundamental studies to applications

Liu, Ruixue; Fraylich, Michael; Saunders, Brian R.

doi:10.1007/s00396-009-2028-x

Cited by 451 publications

(347 citation statements)

References 118 publications

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“…Polymers that exhibit "lower critical solution temperature" (LCST) behavior are soluble in water below their LCST 3,7,8 due to effective hydration of the polymer based on hydrogen bonds between the polymer and the solvent. With increasing temperature, the hydrogen bonds are weakened resulting in dehydration when the LCST is reached.…”

Section: ' Introductionmentioning

confidence: 99%

Poly(2-cyclopropyl-2-oxazoline): From Rate Acceleration by Cyclopropyl to Thermoresponsive Properties

et al. 2011

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There is a high potential for thermoresponsive polymers to be used in various applications, such as drug delivery systems 1À5 and separation processes, 6,7 and, therefore, these materials received significant attention over the last few years. Polymers that exhibit "lower critical solution temperature" (LCST) behavior are soluble in water below their LCST 3,7,8 due to effective hydration of the polymer based on hydrogen bonds between the polymer and the solvent. With increasing temperature, the hydrogen bonds are weakened resulting in dehydration when the LCST is reached. This entropically driven phase transition, i.e., release of water molecules, leads to a collapse of the hydrophobic polymer chains and the formation of aggregates. Therefore, the LCST can be tuned, e.g., by variation of the polymer side chains or by copolymerization with other monomers, as fully explored for the most widely studied thermo-responsive polymer, poly(N-isopropylacrylamide) [PNIPAM]. 3,6,9,10 Poly(2-oxazoline)s with methyl, ethyl, isopropyl, or n-propyl side chains are water-soluble and, except for the most hydrophilic poly(2-methyl-2-oxazoline) (pMeOx), show LCST behavior in water. 11,12 The cloud points (CP) of these poly(2-oxazoline)s increase with increasing hydrophilicity and depend on the degree of polymerization (DP) and concentration. 13À15 The CP can easily be tuned by copolymerization of various 2-oxazoline monomers, as well as by controlling the length and end groups. 16À19 Poly(2-ethyl-2-oxazoline) (pEtOx) is known to only reveal a CP when the DP is above 100, since smaller polymer chains are soluble up to 100°C. 15 Poly(2-isopropyl-2-oxazoline) (piPropOx) is an interesting thermoresponsive polymer, since its CP is close to body-temperature, making it suitable for biomedical applications. 20 However, due to its semicrystallinity the thermo-responsiveness becomes irreversible after annealing above the LCST. 21À23 Poly(2-n-propyl-2-oxazoline) (pnPropOx) is amorphous but has a lower LCST of ∼24°C. 15 In addition, the rather low T g of ∼40°C, which decreases in the presence of water, makes it difficult to handle and to store the polymer at ambient temperature. Therefore, an alternative thermo-responsive poly(2-oxazoline) with a reversible critical temperature close to body temperature is desired.Besides linear poly(2-oxazoline)s, we recently also reported comb polymers containing oligo(2-ethyl-2-oxazoline) (OEtOx) sidechains and a methacrylate (MA) backbone as thermo-responsive ABSTRACT: The synthesis and microwave-assisted living cationic ring-opening polymerization of 2-cyclopropyl-2-oxazoline is reported revealing the fastest polymerization for an aliphatic substituted 2-oxazoline to date, which is ascribed to the electron withdrawing effect of the cyclopropyl group. The poly(2-cyclopropyl-2-oxazoline) (pCPropOx) represents an alternative thermo-responsive poly(2-oxazoline) with a reversible critical temperature close to body temperature. The cloud point (CP) of the obtained pCPropOx in aqueous solution was evaluated i...

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Section: ' Introductionmentioning

confidence: 99%

Poly(2-cyclopropyl-2-oxazoline): From Rate Acceleration by Cyclopropyl to Thermoresponsive Properties

et al. 2011

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“…As it is known that thermoresponsive 44 polymers offer control over viscosity by temperature variation, the abovementioned polymer has been functionalized with NIPAMbased blocks. Several PAM-b-PNIPAM block copolymers were prepared according to Scheme 1B.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Acrylamide Homopolymers and Acrylamide–N-Isopropylacrylamide Block Copolymers by Atomic Transfer Radical Polymerization in Water

et al. 2012

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Atomic transfer radical polymerization (ATRP) of acrylamide has been accomplished in aqueous media at room temperature. By using methyl 2-chloropropionate (MeClPr) as the initiator and tris[2-(dimethylamino)ethyl]amine (Me 6 TREN)/copper halogenide (CuX) as the catalyst system, different linear polyacrylamides with apparent molecular weights up to >150 000 g/mol were synthesized with dispersities as low as 1.39. The molecular weights agreed well with the theoretical ones at relatively low-medium monomer/initiator ratios (<700:1). Initial chain extension experiments (isolated macroinitiator) resulted in a polymer with bimodal distribution. However, in situ chain extension experiments, carried out by addition of a second fresh batch of monomer to the reaction mixture, confirmed the living nature of the polymerization. By adding a fresh batch of monomer to a linear macroinitiator (M n = 22 780 g/mol, PDI = 1.42) in solution, an increase in the molecular weight up to 30 220 g/mol (PDI = 1.64) was observed. In addition, linear polyacrylamides were used as macroinitiators for the synthesis of block copolymers polyacrylamide-b-poly(N-isopropylacrylamide).

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“…Hydrogels used in tissue engineering should have low viscosity before injection and should be gelling fast in the physiological environment of the tissue, and the most important is gelling (sol-gel transition) by cross-linking, which may take place when producing them in vitro and in vivo during injection. Physical cross-linking is used in particular in the case of poly(N-isopropylacrylamide) (poly(NIPAAM)), which may be used in tissue engineering after introducing acrylic acid (AAc) or PEG [460,461] or biodegradable polymers, including such as chitosan, gelation, hyaluronic acid and dextran [462][463][464][465][466] to block copolymers, such as poly(ethylene oxide) PEO-PPO-PEO (Pluronic), poly(lactide-co-glycolide) PLGA-PEG-PLGA, PEG-PLLA-PEG, polycaprolactone PCL-PEG-PCL and PEG-PCL-PEG [467][468][469][470][471], and also agarose (a polysaccharide polymer material, extracted from seaweed as one of the two principal components of agar) [459], as thermo-sensitive systems [472], to avoid the use of potentially cytotoxic ultraviolet radiation. Poly(NIPAAM) and block copolymer hydrogels may undergo cross-linking as a consequence of temperature and pH acting at the same time, as in the case of acrylates [473,474], such as 2-(dimethylamino)ethyl-methacrylate (DMAEMA) or 2-(diethylaminoethyl) methyl methacrylate.…”

Section: Selection Of Technologies Of Implantable Devices In Regeneramentioning

confidence: 99%

Introductory Chapter: Multi-Aspect Bibliographic Analysis of the Synergy of Technical, Biological and Medical Sciences Concerning Materials and Technologies Used for Medical and Dental Implantable Devices

Dobrzański¹

2018

Biomaterials in Regenerative Medicine

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Thermoresponsive copolymers: from fundamental studies to applications

Cited by 451 publications

References 118 publications

Poly(2-cyclopropyl-2-oxazoline): From Rate Acceleration by Cyclopropyl to Thermoresponsive Properties

Poly(2-cyclopropyl-2-oxazoline): From Rate Acceleration by Cyclopropyl to Thermoresponsive Properties

Acrylamide Homopolymers and Acrylamide–N-Isopropylacrylamide Block Copolymers by Atomic Transfer Radical Polymerization in Water

Introductory Chapter: Multi-Aspect Bibliographic Analysis of the Synergy of Technical, Biological and Medical Sciences Concerning Materials and Technologies Used for Medical and Dental Implantable Devices

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