Probing Polymer Chain Folding in Solution Using Second Harmonic Light Scattering was written by Sarkar, Ramkrishna;Mishra, Kamini;Harshita;Das, Puspendu Kumar;Ramakrishnan, S.. And the article was included in Langmuir in 2021.Quality Control of 15-Bromopentadecanoic acid This article mentions the following:
Periodically grafted amphiphilic copolymers (PGACs) were earlier shown by us to adopt a zigzag folded conformation in the solid state, which enabled the backbone and pendant segments to segregate and occupy alternate layers in a lamellar structure. The conformational transition from a random coil to a zigzag folded chain in solution is an interesting problem, which is largely unexplored. To examine this, an orthogonally clickable parent polyester was sequentially clicked with two types of poly(ethylene glycol) (PEG) segments: one is a simple PEG and the other is a PEG that carries a dipolar chromophore. These two hydrophilic PEG segments, installed in a periodic and alternating fashion along the hydrocarbon-rich (HC) polyester backbone, ensure that the Janus folded chains are formed upon folding and carry chromophoric dipoles oriented along the same direction, thereby generating a large net dipole. The folding-induced alignment of chromophores in solution was followed using second harmonic light scattering (SHLS), wherein the intensity of the frequency-doubled scattered light (I2ω) is measured. Folding was induced by adding a polar solvent, like methanol, to a chloroform solution of the polymer; methanol desolvates the HC backbone but solubilizes the pendant PEG segments, thus inducing folding. The second harmonic intensity (I2ω) increased initially with methanol concentration and then saturated; in contrast, I2ω remained invariant with the solvent composition in the case of an analogous model chromophore. Furthermore, in a model PGAC carrying chromophore-bearing PEG segments on every repeat unit, I2ω decreased with increasing methanol composition, revealing the formation of a centrosym. folded chain, wherein the chromophoric dipoles on either side cancel each other. Thus, this study clearly reveals that the zigzag chain folding of PGACs can be induced by a segment-selective solvent, resulting in the rather elusive directional ordering of chromophoric dipoles in solution In the experiment, the researchers used many compounds, for example, 15-Bromopentadecanoic acid (cas: 56523-59-2Quality Control of 15-Bromopentadecanoic acid).
15-Bromopentadecanoic acid (cas: 56523-59-2) belongs to organobromine compounds. Most of the natural organobromine compounds are produced by marine organisms, and several brominated metabolites with antibacterial, antitumor, antiviral, and antifungal activity have been isolated from seaweed, sponges, corals, molluscs, and others. In the pharmaceutical industry organo bromine derivatives are used as sedatives, vasodilators, antiseptic agents, and anticancer agents.Quality Control of 15-Bromopentadecanoic acid
Referemce:
Bromide – Wikipedia,
bromide – Wiktionary