Preparation and characterization of poly(ethylene glycol)-block-poly[e-(benzyloxycarbonyl)-L-lysine] thin films for biomedical applications
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Date
2014
Authors
Izunobi, J. U.
Geever, L. M.
Higginbotham, C. L.
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Abstract
The nanoscale architectures evident in the thin films of self-assembling
hybrid block copolymers—which are tailored to inherit the advantageous properties
of their constituent synthetic (homo)polymer and polypeptide blocks—have
continued to inspire a variety of new applications in different fields, including
biomedicine. The thin films of symmetric hybrid block copolymer, a-methoxypoly(
ethylene glycol)-block-poly[e-(benzyloxycarbonyl)-L-lysine], MPEG112-b-
PLL(Z)17, were prepared by solvent casting in five different solvents and characterized
using Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy,
Thermogravimetric analysis, Derivative Thermogravimetric analysis, Differential
Scanning Calorimetry, Contact Angle goniometry, Wide-Angle X-ray Diffraction, and
Scanning Electron Microscopy. Film thickness was estimated to be 51 ± 23 lmby the
‘‘step-height’’ method, using a thickness gauge. Although no significant change to the
block copolymer’s microstructure was observed, its solvent-cast films displayed
divergent physical and thermal properties. The resulting cast films proved more thermally
stable than the bulk but indicated greater block miscibility. Additionally, the thin
films of MPEG112-b-PLL(Z)17 preserved the microphase separation exhibited by the
bulk copolymer albeit with appreciable loss of crystallinity. The surface properties
of the polymer–air interface were diverse as were the effects of the casting solvents.
Oriented equilibrium morphologies are also evident in some of the as-cast thin
films.
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Keywords
As-cast thin films, Biopolymers, Diblock copolymers, Equilibrium structures, Polypeptides, Surface topography