Structural Analysis of Ultrasoft PDMS-g-PDMS Shell-Only Particles

Abstract

We have used anionic polymerization to synthesize polymers of linear and bottlebrush architecture each with a polydimethylsiloxane backbone. The blending of polymer architectures has the effect of changing material properties, e.g., the viscoelasticity, which are connected to the chain conformation. Thus, we explore the conformation of bottlebrush polymers in a linear host melt both as a function of the concentration and for various molecular weights of the linear host matrices. Our bottlebrush polymers are seen as shell-only particles with a negligible core size. We find a substantial influence of the molecular weight of the linear matrices on the structure of the bottlebrushes and their interactions. In samples with a low molecular weight matrix that have the same degree of polymerization as the side chains, the bottlebrush behavior is consistent with an effective theta solvent condition for all concentrations. With increasing molecular weight of the host matrix, this condition is only reached at the highest concentration of the bottlebrush polymers. The increase of the molecular weight of the host matrix leads to a shrinkage of the bottlebrushes and subsequently to a formation of clusters at higher volume fractions. None of the scattering patterns show a pronounced correlation peak; however, decreased forward scattering associated with a structure factor effect is observed.

Influence of Side-Chain Length and Relative Rigidities of Backbone and Side Chains on Glass Formation of Branched Polymers

“…In particular, we study the crossover from linear polymers to comb polymers with side chains of moderate length to bottlebrush polymers, where the side chains can dominate the properties of the polymer material. While the conformational and viscoelastic properties of branched polymers are highly interesting in their own right, ,,,− ,− we focus here on the characteristic properties of polymer glass formation that can be addressed by both the GET and simulation. We first employ the GET to provide analytical calculations of how the segmental structural relaxation time and the extent of collective motion are influenced by the side-chain length in different classes of polymers, along with the general trends of the characteristic temperatures and fragility of glass formation in variation with the side-chain length, thereby greatly extending the previous studies based on the GET. ,, The relative rigidities of the backbone and side chains are shown to be a key factor in dictating the general trends of the characteristic properties of polymer glass formation in variation with the side-chain length.…”

Dynamical Comparison of Different Polymer Architectures—Bottlebrush vs Linear Polymer

“…For our sample, the overall structure is identified as compact spherical and can be well described using the random phase approximation (RPA) with the core–shell form factor as introduced in eq 1 . Hereby, the parameters for the deuterated specie were kept constant at those values reported in Bichler et al 5 for the deuterated PDMS-g-PDMS bottlebrush polymer immersed in a linear PDMS matrix with M n = 8700 g/mol.…”

“…Due to the negligible core size, the core contribution was excluded in the model function and our bottlebrush can be seen as a star polymer. The detailed form factor, P ( Q ), has previously been published in Bichler et al 5 for a similar sample system.…”

“…Our PDMS-g-PDMS bottlebrush sample has been measured in a complete melt state with isotopic labeling, i.e., a mixture of protonated ((h-PDMS)-g-(h-PDMS)) and deuterated ((h-PDMS)-g-(d-PDMS)) bottlebrushes. Since the degree of polymerization of both bottlebrushes is slightly different, the random phase approximation (RPA) 21 with the modified form factors P̃ ( Q ) BB i for the deuterated and protonated PDMS-g-PDMS bottlebrush polymers according to Bichler et al 5 has been used. The volume of the bottlebrushes is calculated as…”

“… 1 − 3 One architecture of interest are bottlebrush polymers, i.e., linear side chains covalently bonded on a linear backbone. This type of polymer is highly customizable regarding its shape, 4 − 7 chemical composition, 4 , 5 , 8 , 9 and grafting density, 10 , 11 i.e., number of side chain per backbone unit, and received great interest in recent times. Due to their versatility, several applications are known, like supersoft elastomers, drug delivery agents, or viscoelasticity modifiers.…”