Relation between molecular properties and macroscopic performance of interpenetrating networks
Abstract
Soft materials are an important area of great technological interest. The use of many gel materials is, however, often restricted due to their weak mechanical performance. One way of improving their properties is by forming interpenetrating networks. An interpenetrating network (IPN) consists of at least two polymer networks that are formed together but are not covalently bonded to each other. These networks have important applications, e.g., in organic solar cells, drug delivery, and tissue engineering. To be able to improve the mechanical properties, one needs to be able to correlate the mechanical properties with the network structure. The difference in cross-linking density means that the two networks that constitute the IPN will behave differently during the deformation. Understanding the mechanical properties of IPNs is thus of fundamental importance in soft matter mechanics.
To investigate more general types of networks, we previously developed a novel algorithm to create a closed network with an unbiased distribution of crosslinking nodes, which has been used to investigate the diffusion of small molecules in crosslinked networks[1]. Applications in the form of the collapse transition of core-shell nanoparticles have also been studied using a similar type of algorithm[2].
Recently, we have also shown that a homogeneous bimodal gel (one network with two types of chains) can show improved mechanical properties compared to a network with chains corresponding the average chain length[3], and that inhomogeneities in the gel structure, in most cases, make the gel weaker, in accordance with experimental observations[4]. (Project SNIC 2016/1-252 and SNIC 2017/1-543.)
In the proposed project, our aim is the study of the mechanical phenomena of interpenetrating networks during deformation in new geometries using molecular simulations. We want to systematically investigate the mechanical strength and deformational behaviour during compressions and extensions during confinement, mimicing e.g. blood vessels or lab on a chip. The mechanical properties will mainly be investigated by analysing the stress-strain properties and network structure. This will be linked to polymer chain orientation and the local deformation in the material on a molecular level, in order to investigate the interplay of the two networks.
A PhD-student is currently implementing a new version of the program for the new geometries, which should be running during the spring of 2019. The cpu-requirement will thus be unevenly distributed during the period of the project. The requirements for cpu time will be small (just for testing) until mid-spring, and the need for time will then increase. We thus anticipate an average of 1200 cph hours per month for this period would be appropriate.
1. N. Kamerlin & C. Elvingson, J. Phys. Condens. Matter, 28, 475101 (2016)
2. N. Kamerlin & C. Elvingson, Macromolecules, 49, 5740 (2016)
3. N. Kamerlin & C. Elvingson, Macromolecules, 50, 7628, 2017
4. N. Kamerlin & C. Elvingson, Macromolecules, 50, 9353 (2017)
