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Thermally-responsive core-shell part...

Zhang, Li.

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Thermally-responsive core-shell particles.

紀錄類型:	書目-語言資料,印刷品 : Monograph/item
正題名/作者:	Thermally-responsive core-shell particles./
作者:	Zhang, Li.
面頁冊數:	194 p.
附註:	Adviser: Andrew Klein.
Contained By:	Dissertation Abstracts International68-07B.
標題:	Chemistry, Polymer. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3270676
ISBN:	9780549107798

Thermally-responsive core-shell particles.
Zhang, Li.

Thermally-responsive core-shell particles. - 194 p.

Adviser: Andrew Klein.

Thesis (Ph.D.)--Lehigh University, 2007.

The objectives of this research are to synthesize poly(N-isopropylacrylamide) (PNIPAM)/polystyrene (PS) core/shell structured latex particles, to understand their core/shell formation mechanism, and to apply this methodology to the preparation of other core/shell structured particles. By encapsulating PNIPAM particles within a rigid polymer, these core/shell particles can potentially be utilized in areas such as micro-reactors, drug delivery systems, biological systems, and coatings. Thermosensitive PNIPAM, with a volume phase transition temperature (VPTT) of &sim;35°C, can contain as high as 95 wt% water and hence essentially function as micro-water reservoirs.

ISBN: 9780549107798Subjects--Topical Terms:

1018428
Chemistry, Polymer.

Thermally-responsive core-shell particles.
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245 1 0 $a Thermally-responsive core-shell particles.
300 $a 194 p.
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500 $a Source: Dissertation Abstracts International, Volume: 68-07, Section: B, page: 4517.
502 $a Thesis (Ph.D.)--Lehigh University, 2007.
520 $a The objectives of this research are to synthesize poly(N-isopropylacrylamide) (PNIPAM)/polystyrene (PS) core/shell structured latex particles, to understand their core/shell formation mechanism, and to apply this methodology to the preparation of other core/shell structured particles. By encapsulating PNIPAM particles within a rigid polymer, these core/shell particles can potentially be utilized in areas such as micro-reactors, drug delivery systems, biological systems, and coatings. Thermosensitive PNIPAM, with a volume phase transition temperature (VPTT) of &sim;35°C, can contain as high as 95 wt% water and hence essentially function as micro-water reservoirs.
520 $a Crosslinked, monodisperse PNIPAM particles were first synthesized by precipitation polymerization. The particle size was measured by dynamic light scattering (DLS), capillary hydrodynamic fractionation (CHDF), and transmission electron microscopy (TEM). The particles had a VPTT of 34.9°C and a T g of 154.4°C. Linear PNIPAM produced during the synthesis was separated and measured. Two different polymerization methods were used to prepare PNIPAM/PS core/shell particles, a multi-stage process and a semi-batch process. In both processes, uniform "raspberry" structures were obtained in which polystyrene formed small domains on the surface of the PNIPAM particles. The resulting particles were characterized by DLS, CHDF, TEM, and density gradient experiments. It was found that the resulting particle size did not change as a function of temperature, which indicated that the PNIPAM was encapsulated by the PS. To smooth the surfaces of these "raspberry" structured particles, solvent swelling and heat treatment post-processes were investigated. The heat treatment post-process produced smooth surfaces while maintaining PNIPAM in the core of the particles. From the mechanism study on the "raspberry" structure formation, it was found that polystyrene particles were first formed in the aqueous phase and then heteroflocculated on the PNIPAM particles. The linear PNIPAM generated in situ may function as a stabilizer for the PS particles during this process. The PS domains were found to be strongly attached to the PNIPAM particles. In addition, this heteroflocculation mechanism has been applied to three different systems: (1) PNIPAM particles and PS particles and (2) PNIPAM particles and silica particles.
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791 $a Ph.D.
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