O ptically active polymers are very useful as chiral packing materials for optical resolution of various racemates. 1 Circular dichroism (CD) is of critical importance for evaluation of their chirality. Although these types of polymers have been evaluated in solution state, their practical applications are commonly with them in solid state, such as powders and membranes. Evaluation in solid state may directly provide chiral information about the packing materials and make it more reliable. Nanoporous materials or small-sized particles would be especially useful for optical resolution because the extremely high surface area-to-volume ratio could lead to an amplified interaction between the chiral packing material and racemic mixture, thus enhancing the optical resolution. 2 In this respect, optically active nanoporous nanoparticles should be one of the best candidates for highly advanced chiral packing materials. However, a facile preparation and evaluation of such elegant materials should be a great challenge.Among the many types of conjugated polymers, poly-(diphenylacetylene) (PDPA) derivatives are particularly unusual for the following reasons. First, PDPAs are amorphous and exist in a glassy state, depending on the alkyl side chain length. 3 Owing to their amorphous nature and low density, these polymers have relatively large fractional free volumes in the bulk solid state. 4 Second, PDPA derivatives provide highly porous and extremely thin nanofibers from electrospinning or freeze-drying of the polymer solution. 5 The nanoporous network structure is thought to be a result of abrupt phase separation or spinodal decomposition between the polymer and solvent. The porous structure is also very stable, both thermoand hydrodynamically, and is permanently maintained because of the stiff and rigid backbones of PDPAs. Third, the achiral PDPA derivative can be readily converted into optically active materials by heating it in a chiral solvent (chiral solvent annealing, CSA) such as limonene or pinene. 6 Nanoprecipitation (NP) is a very useful and facile method to prepare nanoparticles from conjugated polymers. 7 These polymer particles are referred to as conjugated polymer nanoparticles (CPNs). The principle mechanism for the formation of CPNs in the NP process is abrupt solvent quenching in water, which leads to phase separation between the polymer and solvent. 8 The theoretical product yields of CPNs in the NP process are quantitative, although the process should be conducted in a considerably dilute solution, thus requiring large amounts of solvent and water. Moreover, this method provides much smaller-sized nanoparticles relative to other methods such as emulsion.In this study, we prepared optically active CPNs from CSA and subsequent NP using a PDPA derivative. The solvent chirality was readily transferred to the PDPA simply by annealing it in chiral limonene solution. During the NP process, the chirality-transferred polymer chains came to a standstill with the side phenyl rings being fully relaxed, thus providi...
Highly advanced phase-change hybrids (PCHs), which consist of a phase-change material and conjugated polymer, were developed for new sensor and actuator applications. PCH films with excellent characteristics were obtained simply by depositing various molten paraffin waxes (PWs) in situ onto poly(diphenylacetylene) (PDPA) films with extremely large fractional free volumes. The phase-change enthalpy of the PWs in the hybrid films was quite high and remained constant over prolonged use. The PCH films underwent critical changes in both fluorescence (FL) intensity and color during the phase change of the PWs, which facilitated various sensor applications such as highly reversible writing/erasing, fingerprinting and array-type thermometer usage. In addition, a biaxially oriented polypropylene (BOPP)-supported PCH film exhibited extremely fast and highly reproducible thermomechanical actuation with reversible curling/uncurling during the phase change of the PWs. These findings will be useful for developing novel PCH materials with highly advanced functions and applications.
have been developed for in vitro and in vivo bioimaging applications. CPDs have attracted considerable attention, because of their potential benefi ts such as relatively facile preparation, high fl uorescence (FL) emission quantum effi ciency, photostability, and low cytotoxicity. [ 2a ] However, CPDs still have some drawbacks, because of the characteristic electronic structures of conjugated polymers. First, in general, π-conjugated polymers have planar geometries and strong intermolecular interactions, because of the extremely stiff and rigid main chains, resulting in highly face-to-face chain packing in the solid state. [ 5 ] Although such an intermolecular π-stacked structure is essential for effective charge-carrier transport in the active layer in thin-fi lm organic optoelectronic devices, [ 6 ] the cofacial packing structure signifi cantly reduces the FL quantum effi ciency in bulk solid fi lms, because it produces crystal domains, and the formed intermolecular excimers have an extremely low transition energy in non-radiative processes. [ 7 ] CPDs are no exception to this rule. [ 2,8 ] Signifi cant FL attenuation has been observed in aqueous colloidal solutions compared with the usual organic solutions. Secondly, although CPDs have much higher photostabilities compared with other fl uorescent materials such as organic dyes [ 9 ] and green fl uorescent In this paper, specifi c molecular design rules are proposed for highly fl uorescent, photostable, conjugated polymer dots (CPDs) applicable for the bioimaging of live cells. CPDs are prepared by nanoprecipitation in water using polydiphenylacetylene (PDPA) derivatives and commercial conjugated polymers. Among these, an amorphous, glassy-state PDPA derivative provides highly porous, coarsened nanoparticles. The nanoparticles are dispersed very well in water, and the polymer chains are either hydrodynamically or thermodynamically stable, with a fully relaxed intramolecular stacked structure. This leads to effective radiative emission decays by restraining collisional quenching and vibrational relaxation to achieve an extremely high fl uorescence (FL) quantum effi ciency. The FL emission quantum yield is as high as 0.76, which is the highest value among those reported for conventional CPDs. The PDPA-based CPD has a very low photobleaching quantum yield (∼10 −9 ), because of its relatively high ionization potential. This aqueous colloidal solution is useful for bioimaging plant and mammalian cells. The excellent FL quantum effi ciency, photostability, and cellular uptake suggest that the present CPD is a very promising probe for bioimaging, particularly for long-term imaging and tracking in live cells or experimental animals.Recently, a wide range of fl uorescent nanoparticles such as inorganic semiconductor quantum dots, [ 1 ] conjugated polymer dots (CPDs), [ 2 ] conjugated polyelectrolyte dots, [ 3 ] and carbon dots [ 4 ]
This paper reports a unique fluorescence (FL) response and diverse applications of conjugated polyelectrolyte (CPE) through nonelectrostatic interaction with appropriate (bio)surfactants in an immiscible two-phase system. A sulfonated microporous conjugated polymer (SMCP) with a conformation-variable intramolecular stacked structure was used as the CPE film. Despite the extremely high hydrophilicity, the SMCP film responded significantly to the hydrophobic circumstances, either physicochemically or electronically, in the presence of water-in-oil (w/o)-type nonionic surfactants with appropriate hydrophile-lipophile balance (HLB) values. The polymer film became fully wet with hydrophobic solvents due to the addition of small amounts of (bio)surfactant to reveal remarkable FL emission enhancement and chromism. Microcontact and inkjet printing using the SMCP film (or SMCP-adsorbed paper) and the surfactant solution as substrate and ink, respectively, provided high-resolution FL images due to the distinctive surfactant-induced FL change (SIFC) characteristic. Moreover, the additional electrostatic interaction of SMCP film with oppositely charged surfactants further enhanced the FL emission. Our findings will help comprehensive understanding of the nonelectrostatic SIFC mechanism of CPEs and development of novel SIFC-active materials.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.