Tunable Helical Assemblies of l-Alanine Methyl Ester-Containing Polyphenylacetylene

Abstract

The self-assemblying behaviors of L-alanine methyl ester-containing polyphenylacetylene (PPA-Ala, in Chart 1 ) were investigated upon the evaporation of its solvent on mica and on air/water interfaces. The introduction of chiral amino acid attachments to the polyphenylacetylene backbone induced a helical conformation of the backbone, which was stabilized by various noncovalent interactions, especially hydrophobic effect and hydrogen bonds. The helicity of the polymer was further amplified in its higher-order self-assemblies as the formation of helical fibers on the surface of mica upon natural evaporation of its THF solution. By LB technique, the polymer chains were guided to form ordered parallel ridges and highly aligned, with their helical conformation still remaining. The reorganization of the chiral polymer chains on air/water interface was associated with the additional hydrophobic effect of PPA-Ala on an air/water interface. The polymer backbones had to adopt different arrangements to minimize their contact with water, and this adjustment led to the formation of aligned polymer ridges under proper surface pressure.

Annular cracks in thin films of nanoparticle suspensions drying on a fiber

“…Since the evaporation causes the film thickness to decrease, the particle volume fraction increases as: φ(t) = φ0 1−Vet/h0 . For our silica dispersion, both viscoelasticity characterization [20] and Small Angle X-ray Scattering study [19] reflect a jamming of the particles for φ c 0.35. As a result we can estimate the consolidation time τ cons as φ(τ cons ) = φ c .…”

Chiral nanostructure in polymers under different deposition conditions observed using atomic force microscopy of monolayers: poly(phenylacetylene)s as a case study

“…Next, by compressing the water surface, the surface pressure of the polymers gradually increases until it reaches a point where a compact polymer monolayer is formed (20 mN/m for poly-(L)-27 76 and 40 mN/m for poly-(L)-28). 78 The process can be visualized through the isotherms that exhibit two regions: the low surface pressure region -lower than 15 mN/m), where the surface pressure region gradually increases with compression-, and the high surface pressure region -higher than 15 mN/m, where the surface pressure abruptly increases with compression-.…”

“…78 The process can be visualized through the isotherms that exhibit two regions: the low surface pressure region -lower than 15 mN/m), where the surface pressure region gradually increases with compression-, and the high surface pressure region -higher than 15 mN/m, where the surface pressure abruptly increases with compression-. The limiting area for poly-(L)-27 76 The monolayer formed in this way is then transferred to the surface of freshly cleaved mica, with its hydrophilic side facing the solid support and the hydrophobic part exposed to the air. AFM showed the presence of well-ordered 2D crystals although the quality of the images was not enough to obtain the helical sense, pitch or packing angle of either poly-(L)-27 or poly-(L)-28 ( Figure 16).…”

Preparation of optically active substituted polyacetylene@CdSe quantum dots composites and their application for low infrared emissivity

“…[22][23][24]. Many studies have been conducted on the synthesis of SPAs derived from chiral amino acids because they exhibit biocompatibility, biodegradability, optical activity, and diverse active functional groups [25][26][27][28]. The amino acidbased moieties at the pedants compete with each other and their chiral information is transmitted to the polymer backbone, leading to dynamic helical secondary structures of SPA chains.…”