Photopolymerization and photoprocessing are core technologies for molding and tuning polymer materials. However, they are incompatible with single materials owing to their contradictory photoreactivity. Herein, an acid-induced photocleavable crosslinker, a platinum–acetylide complex covered by permethylated cyclodextrins, enables the fabrication of photoprocessable materials via photopolymerization with N-(2-hydroxyethyl)acrylamide. The polymer networks are molded by 365 nm irradiation as well as softened and degraded by a cooperative reaction with HCl as an acidic additive under 365 nm UV light, or 470 nm visible light in the presence of a photosensitizer. Moreover, the crosslinker is applied to a photoadhesive triggered by 365 nm irradiation. The adhesion is detachable on-demand through acid-induced photodegradation with the same wavelength and intensity of irradiation. Thus, acid-induced photocleavage allows the integration of light-induced molding and processing under various lights of various wavelengths, opening up new strategies for polymer technologies. 相似文献
Four new photoinitiators (PI's) containing various phenylamine-based groups as chromophores and oxime ester (OXE) as initiating groups are proposed for the free radical polymerization, the cationic polymerization, and interpenetrated polymer networks upon visible light exposure using a light emitting diodes at 405 nm. These compounds showed outstanding polymerization photoinitiation ability, that is, high-polymerization rates and good final reactive function conversions were obtained. The chemical mechanisms by which these OXE's generate reactive species were investigated through different techniques including real-time Fourier transform infrared spectroscopy, UV–visible spectroscopy, fluorescence (time-resolved or steady state) as well as cyclic voltammetry. Markedly, the proposed structures can be used as thermal initiators indicating all of them can be polymerized under suitable reaction temperature. In addition, due to their high efficiency, these optimized PI's were found to be useful @405 nm for both direct laser write and 3D printing applications. 相似文献
A stereocontrolled degradable polymer was synthesized via living cascade enyne metathesis polymerization. Highly stereodefined N,O-acetal-containing enyne monomers were prepared using the Pd-catalyzed hydroamination of alkoxyallenes and ring-closing metathesis. The resulting chiral polymer exhibited a narrow dispersity window. Block copolymers were prepared not only by sequentially adding nondegradable and degradable monomers but also by using enantiomerically different monomers to produce stereocontrolled blocks. Owing to the hydrolyzable N,O-acetal moiety in the backbone structure, the resulting polymer could degrade under acidic conditions generated using various acid concentrations to control the degradation. Additionally, the aza-Diels–Alder reaction modified the polymer without losing the stereochemistry. 相似文献
For polymer synthesis upon visible light, actual photoinitiator operates in a restricted part of the spectrum. As a consequence, several photoinitiators are necessary to harvest all of the emitted visible photons. Herein, 2,7‐di‐tert‐butyldimethyldihydropyrene is used for the first time as a multicolor photoinitiator for the cationic polymerization of epoxides. Upon addition of diphenyliodonium hexafluorophosphate and optionally N‐vinylcarbazole, the originality of this approach is to allow efficient monomer conversions under various excitation light sources in the 360–650 nm wavelength range: halogen lamps, and light‐emitting and laser diodes. The synthesis of an interpenetrated polymer network from an epoxide/acrylate blend using a red light at 635 nm is also feasible. The formed polymer material exhibits a photochromic character.
Efficient surface functionalization of cellulose nanocrystals (CNC) with hydroxyl butyl acrylate monomer (HBA) was carried on under mild condition using N,N′-carbonyldiimidazole as an activator. The grafting of the acrylic monomer was shown to bring about the high yield grafting of polymer chains on the functionalized CNC during in situ polymerization process. Surface functionalization of CNC with HBA and the polymer grafting on the modified CNC were confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Nanocomposite film prepared from in situ polybutylmethacrylate polymerization process using HBA functionalized nanocrystals exhibited high transparency degree here assigned to improved dispersion. DMA analysis proved that the best mechanical/rheological performance is obtained for HBA–CNC contents of 4 %. 相似文献
Advanced tools for cell imaging are of great interest for the detection, localization, and quantification of molecular biomarkers of cancer or infection. We describe a novel photopolymerization method to coat quantum dots (QDs) with polymer shells, in particular, molecularly imprinted polymers (MIPs), by using the visible light emitted from QDs excited by UV light. Fluorescent core–shell particles specifically recognizing glucuronic acid (GlcA) or N‐acetylneuraminic acid (NANA) were prepared. Simultaneous multiplexed labeling of human keratinocytes with green QDs conjugated with MIP‐GlcA and red QDs conjugated with MIP‐NANA was demonstrated by fluorescence imaging. The specificity of binding was verified with a non‐imprinted control polymer and by enzymatic cleavage of the terminal GlcA and NANA moieties. The coating strategy is potentially a generic method for the functionalization of QDs to address a much wider range of biocompatibility and biorecognition issues. 相似文献
Photocontrolled surface‐initiated reversible complexation mediated polymerization (photo‐SI‐RCMP) was successfully applied to fabricate concentrated polymer brushes with complex patterning structures. Positive‐type patterned polymer brushes were obtained by photo‐SI‐RCMP under visible light (550(±50) nm) using photomasks. A particularly interesting finding was that negative‐type patterned polymer brushes were also obtainable in a facile manner. A nonspecial UV light (250–385 nm) enabled the preparation of pre‐patterned initiator surfaces in a remarkably short time (1 min), leading to negative‐type patterned polymer brushes. Based on this unique selectivity between visible and UV light, the combination of two patterning techniques enabled the preparation of complex patterned brushes, including diblock copolymers, binary polymers, and functional binary polymers, without multistep immobilization of one or more initiators on the surfaces. 相似文献
Two-dimensional carbon nitride (CN) has drawn increasing attention as a conjugated metal-free polymer for photoelectrochemical (PEC) biosensing. However, CN only absorbs ultraviolet and very limited visible light (λ<460 nm), which poses potential risks for biomolecules and also cannot pass through tissue for in vivo detection. Herein, simultaneous exfoliation and functionalization of CN nanosheets (CNNS) with copper phthalocyanine (TsCuPc) simply by mechanical milling, thanks to the delicate π–π interaction between them, is reported. Moreover, due to energy-level matching, an effective donor–acceptor (D-A) interaction with much-improved photocurrent under irradiation with red light (λ>630 nm) was observed for the as-prepared CNNS-TsCuPc. As an example, dopamine in blood was detected by using red light by a CNNS-TsCuPc photoelectrode with uncompromised linear range and detection limit, as well high selectivity. As one of the few successful demonstrations of red-light-responsive PEC sensing systems, this work takes a first step toward future in vivo applications by enriching the optoelectronic properties of CN with task-specific antenna molecules via D-A interaction. 相似文献