Structural Evidence That the Polymerization Rate Dictates Order and Intrinsic Strain Generation in Photocured Methacrylate Biomedical Polymers

Abstract

The influence of reaction rate on the evolving polymer structure of photo-activated dimethacrylate biomedical resins was investigated using neutron and in situ synchrotron X-ray scattering with simultaneous Fourier-transform-near-infrared spectroscopy. Previous studies have correlated the degree of reactive group conversion with mechanical properties, but the impact of polymerization rate on the resultant polymer structure is unknown. Here, we demonstrate that the medium-range structural order at the functional end groups of these materials is dependent on the reaction rate. Accelerating polymerization increases correlation lengths in the methacrylate end groups but reduces the medium-range structural order per converted vinyl bond when compared with more slowly polymerized systems. At faster rates of polymerization, the conformation of atoms at the reacting end group can become fixed into the polymer structure at the onset of autodeceleration, storing residual strain. Neutron scattering confirms that the structural differences observed are reproduced at longer length scales. This effect is not as prominent in systems polymerized at slower rates despite similar final degrees of reactive group conversion. Results suggest that current interpretations of these materials, which extrapolate mechanical properties from conversion, may be incomplete. Accelerating polymerization can introduce structural differences, which will dictate residual strain and may ultimately explain the discrepancies in the predictive modeling of the mechanical behavior of these materials using conventional techniques.

Publication DOI: https://doi.org/10.1021/acs.macromol.9b00133
Divisions: Engineering & Applied Sciences > Electrical, Electronic & Power Engineering
Engineering & Applied Sciences > Aston Institute of Materials Research (AIMR)
Engineering & Applied Sciences
Additional Information: This is an open access article published under a Creative Commons Attribution (CC-BY) License, which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited. Funding: STFC ST/L502510/1.
Uncontrolled Keywords: Organic Chemistry,Polymers and Plastics,Inorganic Chemistry,Materials Chemistry
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Related URLs: https://pubs.ac ... acromol.9b00133 (Publisher URL)
http://www.scop ... tnerID=8YFLogxK (Scopus URL)
PURE Output Type: Article
Published Date: 2019-07-23
Published Online Date: 2019-07-10
Accepted Date: 2019-06-23
Authors: Sirovica, Slobodan
Skoda, Maximillian W A
Podgorski, M.
Thompson, P.
Palin, William M.
Guo, Y.
Smith, Andrew J.
Dewan, K.
Addison, Owen
Martin, Richard A ( 0000-0002-6013-2334)

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