Microspheres prepared from temperature‐sensitive graft polymers

Kitano, Hiromi; Yan, Changhong; Nakamura, Katsunori

doi:10.1002/macp.1991.021921208

Cited by 42 publications

(13 citation statements)

References 11 publications

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“…34 Furthermore, the PSt nanoparticles were applied to the oral peptide delivery system 35 and improvement of immobilization of metal catalyst. 36,37 The catalyst of platinum colloids have shown high activity on recycling in the aqueous hydrogenation of allyl alcohol.…”

Section: Structural Model Of Nanoparticlementioning

confidence: 99%

Thermosensitive Behavior of Poly(N-isopropylacrylamide) Grafted Polystyrene Nanoparticles

Chen

Serizawa

et al. 2003

Polym J

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ABSTRACT:We analyzed the thermosensitive behavior of monodisperse polystyrene (PSt) nanoparticles having different densities and chain lengths of grafted poly(N-isopropylacrylamide) (PNIPAAm) on their surfaces. The PSt nanoparticles were synthesized by free radical copolymerization of styrene monomer with PNIPAAm macromonomers in mixed ethanol/water solvents. The grafted PNIPAAm densities on the PSt nanoparticle surfaces can be controlled by varying polymerization conditions such as reaction temperature and initiator concentrations. The nanoparticle sizes and densities of grafted PNIPAAm on their surfaces significantly affected temperature-response, which was investigated by dynamic laser light scattering. The larger PSt nanoparticle sizes and higher grafted PNIPAAm densities showed a more significant decrease in hydrodynamic diameters when temperature of dispersed solutions was raised above lower critical solution temperature of the linear PNIPAAm. The molecular weight of grafted PNIPAAm on nanoparticle surfaces had no relationship with a visible decrease in hydrodynamic diameter.KEY WORDS Poly(N-isopropylacrylamide) / Macromonomer / Polystyrene Nanoparticle / Thermosensitivity / Dispersion Copolymerization / There has been a geometric increase in the number of publications involving water-soluble poly(Nisopropylacrylamide) (PNIPAAm), because it exhibits a remarkable phase transition in the aqueous solution when temperature is raised above the lower critical solution temperature (LCST). 1-5 For these ingenious applications, the phase transition behavior of PNIPAAm has been also described in the metal colloids 6 and protein conjugation systems. 7 Copolymers containing PNIPAAm with hydrophilic-hydrophobic segments can exhibit the similar phase transition properties in a large range of temperature. 8 The copolymers with acrylic acid units show a pH sensitive property as well as a thermosensitive one. 9 PNIPAAm-based gels also exhibit thermo-reversible swelling properties. 10 They have been exploited to control enzymatic reactions 11 and drug delivery of biomolecules such as proteins of human gamma globulin. 12 On the other hand, when PNIPAAm was grafted on the external surfaces of substrates such as polymeric films and silicons, it acts as a reversible thermovalve for the separation column. 13 The water absorption and electrostatic charge of surfaces can be controlled for a temperature stimulation. 14 Based on the thermosensitivity of PNIPAAm, it may be used as other material fields in order to develop other functionalities.Polymeric particles that have an extremely large surface area are useful because of their potential application, not only in the technological, but also biomedical fields. In order to expand functions of particle surfaces, Okano et al. prepared thermo-responsive polymer nanoparticles with a core-shell micell structure, in which PNIPAAm chains show the coil-to-globule transition at their surface. 15 Makino et al. reported the particle synthesis with the crosslinked PNIPAAm layer by seed polymer...

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Section: Structural Model Of Nanoparticlementioning

confidence: 99%

Thermosensitive Behavior of Poly(N-isopropylacrylamide) Grafted Polystyrene Nanoparticles

Chen

Serizawa

et al. 2003

Polym J

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“…The phase separation on heating is believed as a phase behavior with the lower critical solution temperature (LCST) [3] which is common to all polymer solutions, although it is stilll controversial [4]. This phase transition of PNIPAM has been used in attempts to control the enzymatic activity [5][6][7][8][9], affinity precipitation separation [10,11] and protein recycling systems [12][13][14][15]. Another growing area in which this property has been exploited is a targeted delivery of drugs and chemical agents such as anticancer drugs.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and phase behavior of aqueous poly(N-isopropylacrylamide-co-acrylamide), poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) and poly(N-isopropylacrylamide-co-2-hydroxyethyl methacrylate)

et al. 2006

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Poly(N-isopropylacrylamide) (PNIPAM) and random copolymers of Poly(N-isopropylacrylamide-co-2-hydroxyethyl methacrylate) (PNIPAM-HEMA), poly(N-isopropylacrylamide-co-acrylamide) (PNIPAM-AAm) and poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) (PNIPAM-DMAA) with various volume fractions of NIPAM , were synthesized by radical polymerization. The phase behavior of the polymers in water was investigated by means of optical transmittance and dynamic light scattering. With decreasing , the cloud point temperature T cp for PNIPAM-HEMA decreased whereas T cp for both PNIPAM-AAm and PNIPAM-DMAA increased. Increase of hydrodynamic radius around T cp resulted from the aggregation of the globules of each polymer was observed from dynamic light scattering. The relationships between the reciprocal of T cp of the polymer solutions and 1-were linear for the three copolymers in the experimental range of 0.65 < < 1. The results are discussed from the aspect of the interaction parameters of copolymer solutions.

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“…[17] The microspheres synthesized by starting from polyallylaminegraft-poly(NIPA) copolymer were tried as supports for the covalent immobilization of trypsin. [18] The interaction of thermosensitive NIPA-based polymers with proteins and antibodies has also been investigated. The temperature and pH-sensitive copolymers of NIPA with 4-pentenoic acid were synthesized for possible use in protein conjugation.…”

Section: Introductionmentioning

confidence: 99%