Physicochemical characterization of PEG-based comb-like amphiphilic copolymer structures for possible imaging and therapeutic applications

Comb-like copolymer structures, also known as graft/comb copolymers, have obtained a significant amount of attention in biomedical and industrial applications because of their unique compositional flexibility, which can lead to versatile structures in bulk, melt, and solution states. With biomedical applications (cancer diagnosis and treatment) as the context, this thesis is aimed at characterizing a series of polyethylene glycol (PEG) -based highly adaptable amphiphilic comb copolymer structures in their solution state that can serve as carriers and potentially contrast enhancement agent in magnetic resonance imaging (MRI). To successfully develop and implement such a delivery/contrast agent system, an adequate understanding is needed concerning their physicochemical properties: stability, size, morphology, local structural information, and magnetic resonance characteristics. The stability of these copolymer structures was characterized by their critical micelle concentration (the lower this concentration, the higher the stability), which was determined by total intensity light scattering and surface tension measurement. The size, morphology, and detailed structural information were studied by a combination of techniques, i.e., dynamic light scattering, transmission electron microscopy, cryogenic transmission electron microscopy, and small angle neutron scattering. Furthermore, solutions of polymer structure containing perfluorocarbon blocks were characterized by 19F magnetic resonance spectroscopy to evaluate their application for MRI contrast enhancement. Perfluorocarbon-containing comb copolymers (i.e., PEG-PFC) in solution had a low CMC of about 2 [mu]m. They were found to form two populations of particles - small micelles and large secondary aggregates. Hydrodynamic radius of micelles did not change with polymer concentration, PEG length, sample preparation method, or time after sample preparation. Large secondary aggregates were most likely compound micelles. Sample preparation method, polymer molecular weight, and time after sample preparation could change the proportion of micelles vs. aggregates.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Chemical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2008

Author dc:creator

• Dawson, Jin Zhou

Advisor dc:contributor.advisor

• Clark K. Colton.

• Chemical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/45921

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/45921