Molecular weight distribution of polymers, termed dispersity (Đ), is a fundamental parameter for determining polymer material properties. This paper reports a novel approach for controlling Đ by ...exploiting a temperature‐selective radical generation in organocatalyzed living radical polymerization. The polymers with tailored Đ were synthesized in a batch system without the assistance of an external pump. A unique aspect of this approach is that Đ was tuneable from 1.11 to 1.50 in any segment in diblock, triblock, and multiblock copolymers and in any form of star and brush polymer without segmental or topological restriction. This approach is amenable to various monomers and free from metals and thus attractive for applications. The approach also generated polymer brushes on surfaces with tailored Đ. An interesting finding was that the polymer brushes exhibited unique interaction with external molecules, depending on the Đ value.
Brush up: A novel approach for modulating polymer dispersity was developed. It is based on temperature‐selective organocatalyzed living radical polymerization and enabled dispersity modulation in any segment in linear and branched block copolymers as well as polymer brushes. A dispersity‐dependent size‐exclusion effect to external molecules was observed for the polymer brushes.
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.
Brush up: Positive‐type and negative‐type patterned polymer brushes were obtained by photocontrolled organocatalyzed living radical polymerization in a wavelength‐switchable manner. The two patterning techniques provided a facile method to create complex patterns and functional surfaces.
Liquid vinyl monomers were converted into solid crystals via halogen bonding. They underwent solid‐phase radical polymerizations through heating at 40 °C or ultraviolet photo‐irradiation (365 nm). ...The X‐ray crystallography analysis showed the high degree of monomer alignment in the crystals. The polymerizations of the solid monomer crystals yielded polymers with high molecular weights and relatively low dispersities because of the high degree of the monomer alignment in the crystal. As a unique application of this system, the crystalized monomers were assembled to pre‐determined structures, followed by solid‐phase polymerization, to obtain a two‐layer polymer sheet and a three‐dimensional house‐shaped polymer material. The two‐layer sheet contained a unique asymmetric pore structure and exhibited a solvent‐responsive shape memory property and may find applications to asymmetric membranes and polymer actuators.
Liquid vinyl monomers were converted into solid crystals via halogen bonding. They underwent solid‐phase radical polymerization, yielding polymers with high molecular weights and relatively low dispersities. The monomer crystals were assembled to pre‐determined structures, followed by solid‐phase polymerization, to yield polymer materials with complex structures.
Halogen bonding (XB) has been used to catalyze organic reactions and polymerizations, which is an emerging research area. Reversible complexation mediated polymerization (RCMP) is an XB-catalyzed ...living radical polymerization and is one of the most promising examples of the XB catalysis. RCMP utilizes alkyl iodides as initiating dormant species and electro-donating molecules and ions such as amines, iodide anions, and oxyanions as catalysts. Various initiating dormant species and catalysts were developed, enabiling the synthesis of well-defined homopolymers and block copolymers with complex architectures, chain-end functionalization, photo-polymerization, and industrial application. The use of inexpensive non-metallic catalysts and the accessibility to a wide range of polymer structures are attractive features of RCMP. This mini-review summarizes the current research status of RCMP and its uniqueness brought
via
the XB catalysis.
The development and applications of an organocatalyzed living radical polymerization
via
halogen-bonding catalysis,
i.e.
, reversible complexation mediated polymerization (RCMP), are highlighted.
Ionic liquid (IL)-based gels (ionogels) have received considerable attention due to their unique advantages in ionic conductivity and their biphasic liquid-solid phase property. In ionogels, the ...negligibly volatile ionic liquid is retained in the interconnected 3D pore structure. On the basis of these physical features as well as the chemical properties of well-chosen ILs, there is emerging interest in the anti-bacterial and biocompatibility aspects. In this review, the recent achievements of ionogels for biomedical applications are summarized and discussed. Following a brief introduction of the various types of ILs and their key physicochemical and biological properties, the design strategies and fabrication methods of ionogels are presented by means of different confining networks. These sophisticated ionogels with diverse functions, aimed at biomedical applications, are further classified into several active domains, including wearable strain sensors, therapeutic delivery systems, wound healing and biochemical detections. Finally, the challenges and possible strategies for the design of future ionogels by integrating materials science with a biological interface are proposed.
This review describes the most recent developments in materials design and the advanced features of ionogels, as well as their emerging biomedical applications.
The paper reports the first free-radical solid-phase polymerization (SPP) of acetylenes. Acetylene monomers were co-crystalized using halogen bonding, and the obtained cocrystals were polymerized. ...Notably, because of the alignment of acetylene monomers in the cocrystals, the adjacent C≡C groups were close enough to undergo radical polymerization effectively, enabling the radically low-reactive acetylene monomers to generate high-molecular-weight polyacetylenes that are unattainable in solution-phase radical polymerizations. Furthermore, the SPP of a crosslinkable diacetylene monomer yielded networked two-dimensional conjugated microporous polymers (2D CMPs), where 2D porous polyacetylene nanosheets were cumulated in layer-by-layer manners. Because of the porous structures, the obtained 2D CMPs worked as highly efficient and selective adsorbents of lithium (Li
) and boronium (B
) ions, adsorbing up to 312 mg of Li
(31.2 wt%) and 196 mg of B
(19.6 wt%) per 1 g of CMP. This Li
adsorption capacity is the highest ever record in the area of Li
adsorption.
An air‐tolerant reversible complexation mediated polymerization (RCMP) technique, which can be carried out without prior deoxygenation, is developed. The system contains a monomer, an alkyl iodide ...initiating dormant species, air (oxygen), an aldehyde, N‐hydroxyphthalimide (NHPI), and a base. Oxygen is consumed via the NHPI‐catalyzed conversion of the aldehyde (RCHO) to a carboxylic acid (RCOOH). The generated RCOOH is further converted to a carboxylate anion (RCOO−) by the base. The RCOO− generated in situ works as an RCMP catalyst; the polymerization proceeds with the monomer, alkyl iodide dormant species, and RCOO− catalyst. Thus, the system is not only air‐tolerant but also does not require additional RCMP catalysts, which is a notable feature of this system. (NHPI is used as an oxidation catalyst for converting RCHO to RCOOH.) This technique is amenable to methyl methacrylate, butyl methacrylate, benzyl methacrylate, 2‐hydroxyethyl methacrylate, and styrene, yielding polymers with relatively low‐dispersity (Mw/Mn = 1.20−1.49), where Mw and Mn are the weight‐ and number‐average molecular weights, respectively.
Air‐tolerant reversible complexation mediated polymerization (RCMP) is developed. The system contains a monomer, an alkyl iodide initiating dormant species, air, an aldehyde, N‐hydroxyphthalimide, and an organic base. This air‐tolerant RCMP technique is amenable to methacrylates and styrene.
Cysteamine, which is an inexpensive and non-toxic aminothiol, was successfully employed as a photo-selective chain end transformation agent of iodo-terminated polymer chains (polymer-I). Polymer-I ...was selectively transformed to hydrogen-terminated (polymer-H) and thiol-terminated (polymer-SH) polymers with and without UV irradiation, respectively. This method is applicable to acrylate polymers. This photo-selective reaction offered a single-step preparation of patterned polymer brushes with SH and H chain end functionalities as a unique application.
Four families of oxyanions, i.e. , carboxylate, nitrate, phosphate, and sulfonate, were studied as novel catalysts in living (or reversible deactivation) radical polymerization via oxygen–iodine ...halogen bonding catalysis. Oxyanions with sodium and tetraalkylammonium counter-cations exhibited good catalytic activities and high solubilities in hydrophilic and hydrophobic monomers. These oxyanion catalysts were amenable for methyl methacrylate, functional methacrylates, styrene, and acrylonitrile, and also afforded block copolymers with low dispersities. The catalytic activities of the oxyanions were also theoretically studied using density functional theory (DFT) calculation. The studied four families of oxyanions are abundant in natural and synthetic compounds. Non-toxic natural carboxylates were successfully used to synthesize well-defined biocompatible polymers. The low cost, low toxicity, and accessibility for a range of polymer designs are attractive features for practical use.
A photo-selective chain-end modification of polyacrylate-iodide (polymer-I) was developed. In the presence of a functional primary amine (NH
2
-R-X with an X functionality) and formic acid, by simply ...switching the ultraviolet (UV) light on and off, polymer-I was selectively converted to hydrogen-terminated polymer-H and chain-end functionalized polymer-NH-R-X (polymer-X), respectively. The scopes of the amenable functional X groups and polyacrylates are wide, and hence this method may serve as a general and versatile method for selective chain-end modification. As a useful application, this method was successfully used to fabricate chain-end patterned binary polymer brushes on surfaces. This method is free from metal, amenable to various functionalities, and useful for designing a range of chain-end functionalized polymers and surface-functionalized materials.
A photo-selective chain-end modification of polyacrylate-iodide (polymer-I) was developed. The method was used to generate chain-end patterned polymer brushes.
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