Polymer Diffusion in Microgels with Upper Critical Solution Temperature as Studied by Incoherent Neutron Scattering

6th Meeting of the Spanish Neutron Scattering Association

Ruiz, D. Serrano^1 ; Cristobal, P. Alonso^1 ; Laurenti, M.^1 ; Retama, J. Rubio^1 ; Lopez-Cabarcos, E.^1

Department of Physical-Chemistry II, Faculty of Pharmacy, University Complutense of Madrid, Madrid

28040, Spain^1

关键词: Biological applications;    Continuous phase transitions;    Incoherent neutron scatterings;    Interchain interactions;    Quasi elastic neutron scattering;    Smart drug deliveries;    Temperature increase;    Upper critical solution temperature;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/549/1/012012/pdf
DOI  :  10.1088/1742-6596/549/1/012012

来源: IOP

【 摘 要 】

Poly(acrylic-acrylamide) interpenetrated microgels present continuous phase transition from collapsed to swollen state around 42 °C. The upper critical solution temperature (UCST) of this polymeric system has prompted scientists to consider them candidates for its use in biological applications such as smart drug delivery devices since the swelling of the polymer matrix would permit the release of the drug previously entrapped within the microgels. In these systems the increment of the temperature can break inter-chain interactions, mainly hydrogen bonds, which reduce the elastic tension that stabilizes the microgel, favoring the polymer swelling. The microgel molecular dynamics at the UCST can be investigated using Incoherent Elastic (IENS) and Quasielastic Neutron Scattering (IQNS). From the analysis of the IQNS data we obtained that the diffusion coefficient of the polymer segments depends on the composition of the interpenetrated matrix. Thus, at room temperature, microgels with a polymer composition of 50% of each component present a diffusion coefficient 1·10-12m2/s, while for the microgels formed by only one component the diffusion coefficient is 5.10-10m2/s. This huge difference in the diffusion coefficient is conspicuously reduced when temperature increases, and we attribute this effect to the breaking of the inter-chain interaction. By means of FTIR-ATR analysis we have identified the groups that are involved in this phenomenon and we associate the breaking of the polyacrylic-polyacrylamide interactions with the swelling of the microgels.