Fragmentation of Fiber-like Micelles with a π-Conjugated Crystalline Oligo(p-phenylenevinylene) Core and a Photocleavable Corona in Water: A Matter of Density of Corona-Forming Chains was written by Ma, Chen;Tao, Daliao;Cui, Yinan;Huang, Xiaoyu;Lu, Guolin;Feng, Chun. And the article was included in Macromolecules (Washington, DC, United States) in 2020.Electric Literature of C7H7NO4 This article mentions the following:
Although fiber-like micelles with a crystalline core prepared by living crystallization-driven self-assembly show promising applications in biomedicine, undesirable fragmentation of fiber-like micelles in water usually occurs, which is a frustrating hindrance toward the exploration of their applications. To deepen our understanding on the fragmentation of fiber-like micelles with a crystalline core, we herein developed a strategy to prepare uniform fiber-like micelles with tunable densities of corona-forming chains and systematically examined the influence of the d. of corona-forming chains on the resistance toward micellar fragmentation in water. A block copolymer consisting of a crystalline oligo(p-phenylenevinylene) (OPV5) segment, a hydrophilic poly(N-isopropylacrylamide) (PNIPAM40) block, and a photocleavable o-nitrobenzyl (ONB) junction (OPV5-ONB-b-PNIPAM40, the subscripts represent the (mean) number of repeat unit of each block) was first synthesized. Subsequently, uniform fiber-like micelles with an Ln of 396 nm composed of an OPV core and PNIPAM corona chains were prepared by the self-seeding approach. By taking advantage of photocleavable ONB junctions and varying UV irradiation time, uniform fiber-like micelles with different densities of PNIPAM chains tethered on the surface of micelles were obtained in ethanol. By employing these fiber-like micelles as a model, the influence of d. of PNIPAM chains on the resistance toward fragmentation of micelles in water was investigated. The results showed that pristine micelles without removal of corona chains significantly fragmented with the decrease of length from about 396 to 134 nm in water, whereas micellar fragmentation could be effectively retarded by decreasing the grafting d. of the PNIPAM corona-forming block. For the micelles with the removal of about 73% of PNIPAM chains, almost no micellar fragmentation was observed after aging in water for 15 days. By taking advantage of the structural similarities existing between bottom-brush polymers and fiber-like micelles with a crystalline core, we proposed that as the d. of PNIPAM chains decreased, more space would be provided for remaining PNIPAM chains to adjust their conformation. Consequently, the tension on the OPV core induced by the stress of corona layers of PNIPAM chains decreased. In the experiment, the researchers used many compounds, for example, 3-(Hydroxymethyl)-4-nitrophenol (cas: 60463-12-9Electric Literature of C7H7NO4).
3-(Hydroxymethyl)-4-nitrophenol (cas: 60463-12-9) belongs to alcohols. The oxygen atom of the strongly polarized O―H bond of an alcohol pulls electron density away from the hydrogen atom. This polarized hydrogen, which bears a partial positive charge, can form a hydrogen bond with a pair of nonbonding electrons on another oxygen atom. Under carefully controlled conditions, simple alcohols can undergo intermolecular dehydration to give ethers. This reaction is effective only with methanol, ethanol, and other simple primary alcohols.Electric Literature of C7H7NO4
Referemce:
Alcohol – Wikipedia,
Alcohols – Chemistry LibreTexts