(574f) Atomistic and Mesoscale Modelling of Poly(methyl methacrylate) in Order to Understand Its Structural and Dynamical Properties

Poly(methyl methacrylate), also known as plexiglas or PMMA, is a common polymer that has a vast range of uses and applications. PMMA can occur in isotactic, syndiotactic, or atactic configuration, which affects its physical properties; relevant properties include its glass melting temperature, chain stiffness, miscibility, and surface activity. In this contribution, we present the development and application of a suitable model of PMMA for all three configurations.

Understanding the local potential energy surface and the dynamics of short polymer segments is an important step to utilize PMMA's properties in opening up future chemical modification strategies for new materials. Therefore, we show the results of molecular dynamics simulations performed on PMMA oligomers. The oligomers were composed of various residue lengths using a recently developed force field for saturated and unsaturated alcohols and esters. The simulations performed on the shortest polymer length, made up of three residues, was performed to determine the allowed conformational families of a PMMA triad. Quantum mechanics optimizations were subsequently performed to obtain a more reliable picture of the triad's potential energy surface.

In polymer science, however, the macroscopic properties greatly rely on the entropic contributions to the free energy of a specifically investigated system. Due to the broad range of time and length scales, not all questions can be dealt with at the atomistic level. That is because a detailed treatment of those degrees of freedom that govern small scales computationally prohibits the consideration of the slower modes that determine macroscopic properties. To overcome this problem, coarse graining to mesoscopic models is often applied. At this level, "superatoms" composed of up to ten atoms replace complete chemical repeat units. Therefore, we complement our atomistic study with a model transfer to the mesocale. We will show in detail how the mapping was executed and to which accuracy some structural and dynamical experimental properties could be matched for the various configurations.