Mesoscale Simulation of the Structure of Star Acrylated Poly(ethylene glycol-co-lactide) Hydrogels
- PDF / 252,894 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 33 Downloads / 145 Views
Mesoscale Simulation of the Structure of Star Acrylated Poly(ethylene glycol-co-lactide) Hydrogels Seyed Sina Moeinzadeh and Esmaiel Jabbari Biomimetic Materials and Tissue Engineering Laboratory, University of South Carolina Columbia, SC 29208, U.S.A. ABSTRACT In this work the microstructures of star acrylated poly(ethylene glycol-co-lactide) (SPELA) with different LA:EG ratios in the aqueous solution have been simulated via Dissipative Particle Dynamics (DPD) approach at the mesoscale. The system components were coarse-grained into different beads (set of atoms) which moved according to the Newton’s equations of motion integrated via a modified Velocity-Verlet algorithm. The force acting on each bead, in a specific cutoff distance (rc), was divided into a conservative force (FC), random force (FR), dissipative force (FD), bond force (FS) and bond angle force (FE). The repulsion parameters of the conservative force (αij) were calculated from the solubility parameter of the beads, each of which were extracted from an atomistic molecular dynamics simulation (MD). Simulations showed the formation of micelles with lactide and acrylate beads occupied the core and hydrophilic ethylene oxide segments extending through the water to form the corona. The micelles showed an increasing trend in size and decreasing trend in number density with increase in LA:EG ratio. Results showed that the acrylate density decreased from the center of the micelles to the core surface although the overall amount of acrylates increased due to the increase in volume. Furthermore, the running integration number of acrylate-water beads showed decreasing accessibility of acrylates to water with increasing PLA volume fraction. INTRODUCTION Poly(ethylene glycol) (PEL) macromers are the most widely used polymer for synthesizing biomedical hydrogels [1,2]. However, PEG hydrogels are not biodegradable which limits their use for in vivo applications. Degradable PEGs cane be produced by polymerization of PEG macromers with degradable lactide/glycolide monomers but the aqueous solubility of the degradable macromer strongly depends on the length of the degradable segment [3]. The size and architecture of the PLEG macromer along with the relative size of the hydrophilic EG to the hydrophobic LA segments are of the most important factors controlling the microstructure of these polymers in aqueous solution [4]. The PEL macromers can be chain-terminated with unsaturated acrylate groups to make them amenable to chemical crosslinking [5]. The distribution and accessibility of the reactive groups in the formed microstructures are important parameters with regard to degradation and extent of crosslinking. The star macromers have more reactive groups per unit volume compared to the linear ones which increases the rate of crosslinking at constant initiator concentration. Furthermore, star macromers have lower shear viscosity resulting in the onset of diffusioncontrolled polymerization at higher conversions, leading to the higher extent of crosslinking [6].
93
Diss
Data Loading...
