Melting at Alkyl Side Chain Comb Polymer Interfaces

Abstract

Infrared visible sum frequency generation (SFG) spectroscopy has been used to study structure and melting transition temperatures of alkyl-side chain-acrylate comb polymers at air and solid interfaces. At the air interface, the SFG spectra show methyl bands and two transitions are observed: the first, near the bulk melting temperature, T(m), and the second 10-20 degrees C higher than T(m). The shorter the alkyl side chain, the larger the difference between the two transition temperatures. In contrast, methylene bands are observed at sapphire interface with a single transition near T(m) (C18).

Probing Polymer/Polymer Interfaces

“…Below 50°C, the surface chains at air/Comb interface are crystalline, and the magnitude of the Fermi peak is smaller than the methyl symmetric peak. 6 Therefore, the presence of a higher-intensity Fermi peak at the Comb/hPS and Comb/dPS interfaces suggests the crystallinity of the alkyl side chains is disrupted at these interfaces. The presence of a methylene contribution in the SFG spectra corresponding to a larger population of gauche defects also supports this hypothesis.…”

“…The methyl symmetric, methyl asymmetric, methyl symmetric Fermi resonance, methylene symmetric, and methylene asymmetric vibrational bands are assigned at 2875, 2960, 2935, 2845, and 2915 cm -1 , respectively. 3,6 The peak at 2865 cm -1 is broad and has contributions from methylene and methyl symmetric bands at 2845 and 2875 cm -1 . The peak at 2935 cm -1 is assigned to the Fermi resonance of the overtone bands of the * To whom correspondence should be addressed.…”

“…This technique has been recently used to study a variety of polymer interfaces including polymer/ air, polymer/liquid, and polymer/solid interfaces. [3][4][5][6] Here we report the first SFG measurement of molecular structure at poly(vinyl-N-octadecylcarbamate-co-vinyl acetate)/poly(styrene) (Comb/PS) polymer/polymer interface. The carbamate Comb polymers are widely used as release coatings for pressure sensitive adhesives, and their low adhesion at polymer/polymer interfaces with adhesives is attributed to their interfacial structure.…”

“…The enhancement in SFG signal near critical angles has been used recently to study liquid/ liquid 8 and polymer/solid interfaces. 5,6 Further details of SFG theory and the details of SFG spectrometers have been discussed previously. 9,10 Samples for SFG were prepared by spin coating a film ∼300-nm thick from a 5 wt % solution of hPS (M w ) 108 kg/mol, M w / M n ≈ 1.06 or deuterated PS, M w ) 125 kg/mol M w /M n ≈ 1.13) in toluene onto the surface of a sapphire prism and annealing the film at 110°C under vacuum for 3 h. A second film ∼200 nm thick was then spin-cast on top of the first from a warm 6 wt % solution of Comb (M w ) 70 kg/mol M w /M n ≈ 3.0) in 50/50 mixture of octanol and butanol (both nonsolvents for PS), and the bilayer sample ( Figure 1) was annealed again for 3 h at 110°C under vacuum.…”

Faraday Instability in a Surface-Frozen Liquid

“…Related surface ordering effects were observed in melts of polymers comprising alkyl chains in the backbone or as side chains [10], in liquid alloys [11], and in several liquid crystals [12]. While the structural and thermodynamic aspects of SF have been studied in great detail [13], the influence of surface ordering on macroscopic near-surface flows has received little attention to date in this sizable, technologically-important class of materials.…”