Temperature dependant structural changes in thin films of random semifluorinated PMMA copolymers

Abstract

Semifluorinated (SF) side chain polymers show phase separation between polymer backbone and SF side chains. Due to strong interaction between SF segments the side chains determine the structure behaviour strongly, often resulting in layered structures in which backbones and layers of SF side chains alternate. The interest in this work was directed to find out the dependence of these structures on concentration of SF side chains. Thin films of random copolymers consisting of methylmethacrylate (MMA) and semifluorinated side chain methacrylate (SFMA) segments and with different fluorine content in the perfluoroalkyl side chains (abbreviated as H10F10 and H2F8) were prepared by spin-coating. Phase separation and structure changes were initiated by external subsequent annealing. Corresponding bulk material served as basic information. Generation of ordered structures and variation of film parameters were observed using different X-ray scattering methods (XRR, GIWAXS, and GISAXS). The phase behaviour in bulk is governed by the SF side chain amount and their specific fluorine content which control the self-organization tendency of SF side chains.Additionally, the confinement in thin films generates an orientation of side chains normally to film surface.

Semifluorinated PMMA Block Copolymers: Synthesis, Nanostructure, and Thin Film Properties

“…The formation of sf layers was observed, as seen in the vertical spot at 2.95 nm indicated by the arrow at the top. This value is comparable to that found in random copolymers PMMA‐ co ‐PsfMA . This spot was observed again with weaker intensity in the BCP with d f in the range of d bulk (Figure b), but not in the sample with lower d f (Figure c).…”

X-ray characterization of crosslinked methacrylate copolymers for application as dielectric layers in organic electronics

“…Three series of copolymers were studied (see Table I) having sf side chains of different length (-O-(CH 2 ) 10 -(CF 2 ) 10 F, abbreviated H10F10; -O-(CH 2 ) 2 -(CF 2 ) 8 F, abbreviated H2F8, and -O-(CH 2 ) 2 -(CF 2 ) 6 F, abbreviated H2F6). Based on the knowledge of the ordering behavior of other sfMA copolymers, it was expected that the copolymers with H10F10 side chains form a structure characterized by interdigitation of the sf side chains, while H2F8 and H2F6 copolymers would show a structure where the sf side chains arrange head-to-head (Jehnichen et al ., 2011; Jehnichen et al ., 2013; Pospiech and Jehnichen, 2014; Pospiech et al ., 2016).…”

Semifluorinated Methacrylate Random Copolymers: Phase Transitions and Molecular Dynamics

“…Interestingly, for the relaxation in similar copolymers having H 2 F 8 as side chains (results not shown here) activation energy of 27 kJ/mol and zero activation entropy were found. According to the study of the structure in copolymers having both H 10 F 10 and H 2 F 8 as side chains, in the former case the side chains are interdigitized to form the layer, while in the latter are ordered head to head [25,26]. So, in copolymers with H 2 F 8 as side chains the unit can relax independently from the others, while in the copolymers with H 10 F 10 as side chains there is a sterical hindrance and in order the unit to relax cooperative motions are needed.…”

“…It has been found in previous work that for H 10 F 10 methacrylate copolymers with sfMA contents higher than 25mol% the side chains are organized in well ordered layered structures where chain backbone and side chains alternate [25,26]. Copolymers with sfMA molar contents below 25mol% show only a glass transition, T g , while for higher contents additionally to the glass transition transitions from isotropic to liquid crystalline, T i , and from liquid crystalline to crystalline phase, T m , were found.…”

“…Copolymers with sfMA molar contents below 25mol% show only a glass transition, T g , while for higher contents additionally to the glass transition transitions from isotropic to liquid crystalline, T i , and from liquid crystalline to crystalline phase, T m , were found. The structure of the samples was studied by temperature dependent X-ray techniques and published in [26]. A typical smectic structure is formed at T m <T<T i and negative coefficient of the linear expansion of the layer distance (4,7 to 4,2 nm) was found.…”