Revealing structural evolution occurring from photo-initiated polymer network formation

Abstract

Photopolymerization is a key enabling technology offering spatial and temporal control to allow for future functional materials to be made to meet societal needs. However, gaining access to robust experimental techniques to describe the evolution of nanoscale morphology in photo-initiated polymeric systems has proven so far to be a challenging task. Here, we show that these physical transformations can be monitored and quantified at the nanoscale in situ and in real-time. It is demonstrated that the initial structural features of the liquid precursors significantly affect the final morphology and the physical properties of the resulting solid via the occurrence of local heterogeneities in the molecular mobility during the curing transformation. We have made visible how local physical arrestings in the liquid, associated with both cross-linking and vitrification, determine the length scale of the local heterogeneities forming upon curing, found to be in the 10-200 nm range.

The synchrotron radiation source PETRA III and its future ultra-low-emittance upgrade PETRA IV

“…PETRA III serves a broad user community, covering a very broad range of scientific fields, from physics [1][2][3][4], chemistry [5,6], and biology, to medicine [7,8], materials [9][10][11], geo- [12][13][14][15] and environmental [16,17] science, archaeometry [18], and nanotechnology [19,20]. With this, it makes an important contribution to solving the grand societal challenges, e.g.…”

“…A key strength is to perform experiments in situ and under working conditions, giving insight into processes, e.g. in catalysis [5,6] or materials synthesis [10,31,32]. To date, more than 4700 publications (average journal impact factor 6.0) resulted from research at PETRA III, 23% of which published in journals with an impact factor larger than 7.…”

Controlling network morphology in hybrid radical/cationic photopolymerized systems

“…5 These irregularities can be attributed to the formation during network evolution of nano/microgels which contain high internal cross-link density and relatively low covalent connectivity. 6 The low connectivity manifests through bulk material properties with fracture prone pathways that increase material failure rates in high stress applications. 7 To overcome these challenges, considerable attention has been focused on directing polymer structure to ultimately control the macroscopic properties of photocured materials.…”

Structure Development of the Interphase between Drying Cellulose Materials Revealed by In Situ Grazing-Incidence Small-Angle X-ray Scattering

“…This is an important fundamental process to understand as it defines the physical properties of the majority of the products made from cellulose. Since grazing-incidence small-angle X-ray scattering (GISAXS) was first used to study thin film growth by Levine et al in 1989, it has been successfully utilized to probe the structures of thin films formed at liquid , or solid surfaces. − The structures of different cellulose thin films and the water-induced structural rearrangements of these cellulose films − have also been resolved by GISAXS measurements. Although GISAXS has been successfully applied to these different research areas, its application to study liquid/solid and liquid/liquid interfaces is quite rare.…”