Year: 2002
Type: article
Abstract: Solid-state 13C-NMR spectroscopy has been used to characterize the conformation of the hydrophobic poly(ε-caprolactone) core of a nanoparticle having a cross-linked hydrophilic poly(acrylic acid)/polyacrylamide shell. The amphiphilic nanoparticles were synthesized from the diblock copolymer, poly(ε-caprolactone)121-b-poly(acrylic acid)165 by self-assembly into polymer micelles, followed by cross-linking via condensation reactions between the carboxylic acid groups of the hydrophilic shell and the amine groups of 2,2′-(ethylenedioxy)bis(ethylamine). NMR Experiments performed at −30° on nanoparticles rapidly quenched from 60° show that the core is largely noncrystalline and locally disordered. Heating to 25° results in some crystallization, although far less than that observed for bulk poly(ε-caprolactone) homopolymer. Storage at −30° results in further crystallization and conversion of most rubbery, mobile regions into more rigid, locally ordered amorphous domains. The absence of dipolar coupling between natural-abundance 13C in the poly(ε-caprolactone) core of the nanoparticle, and 15N labels dispersed throughout the cross-linked shell show that the interface between core and shell is sharp. The dipolar coupling measurements were accomplished by 13C{15N} rotational-echo double resonance.
Source: Helvetica Chimica Acta
Authors: Robert D. O'Connor, Qi Zhang, Karen L. Wooley, Jacob Schaefer
Institution: Washington University in St. Louis
Language: English
Subfield: Polymers and Plastics
Field: Materials Science
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W2043412893