Available on-demand - F.SM02.03.11
Late News: Mesoscale Modeling of Controlled Degradation in Hydrogels
Vaibhav Palkar1,Chandan Choudhury1,Olga Kuksenok1
Hydrogel based soft materials with chemical functionalities that allow controlled degradation of the polymer are utilized as active stimuli responsive platforms for numerous applications. As one example, a hydrogel with multiple degradable functional groups that degrade in response to different wavelengths of light enables sequential release of drugs from the network. Herein, we present Dissipative Particle Dynamics (DPD) based simulations of degradation in tetra-arm polyethylene glycol (tetra-PEG ) hydrogels. Controlled degradation can be introduced in these gels via several chemical pathways [2,3]. In our DPD model we use the modified segmental repulsive potential (mSRP ) to avoid unphysical polymer chain crossing and we first establish model parameters that mimic the hydrophilicity of PEG. Further, we use our recently developed framework  to introduce controlled degradation in these gels and measure the fraction of degradable bonds intact during degradation. Our method allows modeling of first order degradation kinetics in these gels. We track the evolution of mass loss from bulk degrading gels and note the occurrence of a slow mass loss regime due to erosion followed by a fast regime due to reverse gelation of the polymer network. We quantify the reverse gel point of these gels by tracking the size of the second largest cluster during degradation. We focus on the effect of finite size on mass loss and reverse gel point calculations and compare these effects with previously developed scaling . The reverse gel point for tetra-PEG hydrogels measured from our simulations corresponds well with the value obtained from percolation theory on a diamond lattice.
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