Observation of Novel Liquid-Crystalline Phase Above the Bulk-Melting Temperature

In this paper, we show that a noncrystalline but ordered smectic-like phase exists above the bulk-melting temperature (T-m) at poly(n-alkyl acrylates)-air interface. The surface ordered phase is one monolayer thick and undergoes a sharp transition from order to disorder 10degreesC above T-m for n=22. The presence of a surface phase that does not exist in the bulk has important implications in the design of thermally responsive adhesives

Machine Learning Decoder for 5G NR PUCCH Format 0

5G cellular systems depend on the timely exchange of feedback control information between the user equipment and the base station. Proper decoding of this control information is necessary to set up and sustain high throughput radio links. This paper makes the first attempt at using Machine Learning techniques to improve the decoding performance of the Physical Uplink Control Channel Format 0. We use fully connected neural networks to classify the received samples based on the uplink control information content embedded within them. The trained neural network, tested on real-time wireless captures, shows significant improvement in accuracy over conventional DFT-based decoders, even at low SNR. The obtained accuracy results also demonstrate conformance with 3GPP requirements.Comment: Submitted to NCC conferenc

Molecular Structure of Hydrophobic Alkyl Side Chains at Comb Polymer-Air Interface

Surface sensitive sum-frequency generation (SFG) spectroscopic technique has been used to study the orientation of alkyl side chains for comb polymers at polymer-air interface. The SFG spectra at 24oC for thick spin-coated polymer films and adsorbed layer (on mica substrate) show strong signals associated with methyl asymmetric and symmetric vibrations indicating ordered methyl terminal groups. However, the ratio of methylene to methyl stretch vibrations is higher for the adsorbed layer than that observed for spin-coated films. This spectroscopic evidence of poor packing of alkyl chains with enhanced gauche defects correlates well with low water contact angles measured for the adsorbed films. In this talk, the surface structure as a function of chain length and temperature will be discussed

Probing Polymer/Polymer Interfaces

Infrared-visible sum frequency generation spectroscopy (SFG) has been used to study the interface between poly(vinyl-N-octadecylcarbamate-co-vinyl acetate) (Comb) and deuterated or hydrogenated polystyrene (dPS or hPS) films. Strong methyl symmetric and Fermi resonance bands associated with the alkyl side chains of the Comb polymer are observed in the SFG spectra. In addition, for Comb/hPS spectra, symmetric and asymmetric vibration modes of phenyl groups are observed. The presence of asymmetric modes indicates the phenyl rings are tilted with respect to the interface normal

Observation of Novel Liquid-Crystalline Phase Above the Bulk-Melting Temperature

In this paper, we show that a noncrystalline but ordered smectic-like phase exists above the bulk-melting temperature (T-m) at poly(n-alkyl acrylates)-air interface. The surface ordered phase is one monolayer thick and undergoes a sharp transition from order to disorder 10degreesC above T-m for n=22. The presence of a surface phase that does not exist in the bulk has important implications in the design of thermally responsive adhesives.</p