Surface ordering in thin films of liquid‐crystalline polymers containing fluorinated and protonated segments: Neutron‐reflectometry study

Abstract

Surface-induced layering of fluorinated and protonated segments in thin films of a main-chain liquid-crystalline polymer, consisting of ␣-methylstilbene, bridged by a fluorinated group was revealed by neutron reflectometry. The layering was driven by the difference in surface energy of the fluorinated and protonated segments and by the inherent ordering of the polymer. The lower-surface-energy fluorinated segments segregated to the air surface, and the protonated segments segregated to the SiO x layer at the Si substrate. The ordering induced by the interface decayed into the film with a characteristic decay length of about 100 Å. The surface-induced periodicity ranged from 15 to 20 Å, which is approximately equal to the molecular dimension of the repeating unit on the polymer backbone. The magnitude of segregation increased upon annealing in the liquid-crystalline temperature range. The segregation was retained upon annealing above the bulk order-disorder transition temperature.

Synthesis of functional polymers—Vinylidene fluoride based fluorinated copolymers and terpolymers bearing bromoaromatic side‐group

“…[(α,β,β‐Trifluorovinyl)oxy]benzene and polymers incorporating such a monomer are very interesting materials62, 63 because of the combination of processability and performance provided by trifluorovinyl ethers, and they have received attention by various research groups64–68 and industries,69–73 and are currently used as materials for the preparation of ion exchange resins,72, 74 ionomer membrane and fuel cell,75–77 microphonic,78 optics,79–82 liquid crystalline,83–85 interlayer dielectrics,86, 87 circuit board laminates,88 and coating applications 89, 90…”

Science and technology of perfluorocyclobutyl aryl ether polymers

“…Specifically, the mesogenic nature of a-methylstilbene containing polymer 7 imparts LC ordering similar to LC epoxy thermoset polymers. 14,133,134 The polymer obtained by thermal cyclopolymerization forms lyotropic lamellar mesophases over a wide range of temperatures and molecular weights. Birefringent textures observed by optical microscopy are consistent with a nematic phase.…”

“…Furthermore, film studies using neutron-reflectometry show self-assembly, producing phase separation of fluorinated segments from the non-fluorinated segments. 134 We have also prepared a new class of thermotropic LC PFCB aryl ether polymers (13) improving the processability of poly(p-phenylene)s (PPPs) through the installation of PFCB group as a solubilizing segment into the PPP main chain. 25 The polymerization induced LC HIGHLIGHT formation mechanism was observed.…”

Influences of chain heterogeneity on instability of polymeric thin films: Dewetting of polystyrenes, polychloromethylstyrenes and its copolymers

“…It has been known that even slight difference of chemical structures such as the system of blended polystyrene/polymethylstyrene can drive the segregation of polymeric chains [42]. Different segments connected via chemical bonds can segregate into different regions by allowing chain organization [1,2,8]. In the system of P(S 0.95 -coClMS 0.05 ) where trace amount of chloromethyl group is covalently bound to the PS chains, the incompatibility is believed to be one important factor that causes the formation of the small holes.…”

“…When polymeric chains are fabricated into thin film, their physical properties tend to deviate from the bulk counterparts, caused by various factors such as interfacial interactions and chain confinement [1,2]. The dominance of interfacial interactions in thin film results in many interesting phenomena such as the increase/decrease of glass transition temperature (T g ) [3][4][5], surface ordering and surface segregation [1,2,[6][7][8]. The decrease of film thickness may also cause an instability, which eventually leads to the dewetting on substrate [1,2,[9][10][11][12][13].…”