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Structural evidence that the polymerization rate dictates order and intrinsic strain generation in photocured methacrylate biomedical polymers

DOI: 10.1021/acs.macromol.9b00133 DOI Help

Authors: Slobodan Sirovica (University of Aston) , Maximilian W. A. Skoda (ISIS Pulsed Neutron and Muon Source) , Maciej Podgorski (University of Colorado Boulder) , Paul B. J. Thompson (ESRF-The European Synchrotron) , William M. Palin (University of Birmingham) , Yilan Guo (University of Alberta) , Andrew J. Smith (Diamond Light Source) , Karun Dewan (University of Birmingham) , Owen Addison (University of Birmingham; University of Alberta) , Richard Martin (University of Aston)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Macromolecules

State: Published (Approved)
Published: July 2019
Diamond Proposal Number(s): 11687 , 14117 , 15319

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.

Subject Areas: Biology and Bio-materials, Chemistry

Instruments: I16-Materials and Magnetism , I22-Small angle scattering & Diffraction

Other Facilities: ESRF