Polymer Journal

Kamigaito, Masami

doi: 10.1038/s41428-022-00680-6pmid: N/A

Metal-catalyzed Kharasch addition or atom transfer radical addition (ATRA) is one of the most efficient radical reactions for controlled syntheses of organic molecules. This reaction proceeds via metal-catalyzed controlled generation of radical species from organic halides, subsequent addition of the radical species to vinyl groups, and capping of the resulting adduct radicals with halogens. Metal-catalyzed radical addition has evolved in various directions and resulted in the development of novel precision radical polymerizations, which allow control over many aspects of vinyl polymer structures, such as molecular weights, terminal groups, architectures, and monomer sequences. This review is focused on the development of metal-catalyzed living radical polymerizations via reversible activation of carbon-halogen bonds, metal-catalyzed step-growth radical polymerizations of designed monomers having an unconjugated vinyl group and a reactive carbon-halogen bond, simultaneous metal-catalyzed chain- and step-growth radical polymerization for syntheses of degradable vinyl copolymers, and vinyl monomer sequence control via combinations of iterative ATRAs and various controlled polymerizations.

Sugihara, Shinji

doi: 10.1038/s41428-022-00698-wpmid: N/A

Vinyl ether (VE) was long believed to be among the monomers that could not be radically homopolymerized. Therefore, to synthesize block copolymers with versatile radically polymerizable monomers, efficient transformation reactions were necessary between living cationic and controlled radical polymerizations. Under such circumstances, some groundbreaking polymerizations have been discovered. One reaction, a metal-free RAFT cationic polymerization, enabled the in situ introduction of the thiocarbonylthio moiety into poly(VE)s. This technique produced block copolymers using both cationic and radical RAFT processes. Advances in research have made it possible to perform radical homopolymerization with hydroxy-functional VE. This achievement was attributed to the hydrogen bonding between the VE oxygen and the hydroxy group that reduced the reactivity of the growing radical. Consequently, RAFT radical polymerization of VE was achieved due to hydrogen bonds and/or cation-π interactions between VE monomers and the propagating radical. Thus, vinyl ether became a radically polymerizable monomer. By using the resulting poly(VE) as a thermoresponsive polymer and as a reactive emulsifier for polymerization-induced self-assembly, various functional polymers and nano-objects can be obtained. This review focuses on the controlled radical polymerization of VEs and the related self-assemblies.

Hiruta, Yuki

doi: 10.1038/s41428-022-00687-zpmid: N/A

The synthesis and application of stimuli-responsive polymer materials have been extensively studied. Among stimuli-responsive polymers, thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm) is the most widely investigated. PNIPAAm-based polymers undergo a reversible hydrophilic/hydrophobic phase transition in response to temperature. In addition, by introducing sites that are responsive to physical and chemical stimuli into PNIPAAm-based polymers, they also undergo phase transitions in response to stimuli, such as light, pH, oxidation/reduction, and enzyme activity. In this focus review, recent advancements in the applications of stimuli-responsive polymers based on PNIPAAm in biomedical fields are summarized, with an emphasis on our own research. In particular, a summary of the design of polymers for application in the separation and purification of (bio)pharmaceutical products and controlled cellular uptake is provided. First, temperature-responsive chromatography with PNIPAAm-modified silica beads is introduced. Thereafter, temperature- and pH-responsive polymers based on PNIPAAm used in imaging and drug delivery applications are discussed. Finally, the conclusions are presented, and future perspectives for the biomedical applications of stimuli-responsive polymers are discussed.

Koda, Yuta

doi: 10.1038/s41428-022-00695-zpmid: N/A

In this focus review, recent developments in unnatural sugar- and protein-based polymers and their future bioapplications are discussed. A new unnatural oligoaminosaccharide carrying N-1,2-glycosidic bonds that cannot be prepared in natural biological systems has been proposed. To prepare the oligomers, a sugar monomer possessing a 2-methyl-2-oxazoline (MeOx) ring was polymerized via cationic ring-opening polymerization. This polymerization did not proceed by the classical MeOx mechanism but by a new mechanism involving sequential SN1-type reactions. This unnatural oligosaccharide was not decomposed by the natural enzymes owing to the unnatural N-1,2-glycosidic bonds, indicating promise in applications as a new class of glycomaterials. Furthermore, technology for stabilizing proteins using protein–polymer conjugations and polymer chain-folding nanoparticles has recently been developed. Amphiphilic/fluorous methacrylate-based random copolymers bearing polyethylene glycol (PEG) and fluorous side chains formed reversible PEG and fluorous compartments in water and 2H,3H-perfluoropentane (2HPFP), respectively. These copolymers were noncytotoxic and successfully conjugated with lysozymes. They also stabilized lysozyme and α-chymotrypsin in 2HPFP, and the enzymes were not denatured after extraction from 2HPFP.

He, Zhipeng; Lv, Wei; Gao, Guoli; Yin, Qinwei

doi: 10.1038/s41428-022-00697-xpmid: N/A

A simple and effective method based on in situ infrared spectroscopy and two-dimensional (2D) correlation analysis was applied to research the chemical changes and curing reaction mechanism of epoxy resin and amine curing agents. It is generally agreed that the epoxy groups in epoxy resin react with amino groups to form new C–N and hydroxyl groups during the curing reaction process. However, detailed information about the curing reaction mechanism of epoxy resin and amine curing agents has rarely been reported. In this work, the curing reaction mechanism can be deeply understood from the results of 2D correlation analysis. Due to the nucleophilic addition reaction of amino and epoxy groups, the nitrogen atoms of primary amines easily combine with the carbon atoms in epoxy groups, which forms new C–N groups. Then, the C–O bonds in epoxy groups break; finally, as the N–H bonds in primary amines break, the hydrogen atoms combine with the oxygen atoms to form new hydroxyl groups.

Tsuji, Hideto; Osanai, Katsuya; Arakawa, Yuki

doi: 10.1038/s41428-022-00682-4pmid: N/A

Here, asymmetric combinations of chiral 2-hydroxyalkanoic acid (2HAA)-based random copolymers with monomer compositions of approximately 50/50, which can form stereocomplex (SC) crystallites, are reported. The copolymer combinations were l-configured individually crystallizable poly(l-lactic acid-co-l-2-hydroxybutanoic acid) [P(LLA-co-L-2HB)] (47/53) or poly(l-2-hydroxybutanoic acid-co-l-2-hydroxy-3-methylbutanoic acid) [P(L-2HB-co-L-2H3MB)] (49/51) and d-configured individually noncrystallizable poly(d-lactic acid-co-d-2-hydroxy-3-methylbutanoic acid) [P(DLA-co-D-2H3MB)] (45/55). The interplanar distance values of each SC crystallite agreed well with those expected from the homopolymer SC crystallites. This finding indicated that all four types of monomer units cocrystallized to form SC crystallites. The melting temperature values of the stereocomplexed P(LLA-co-L-2HB)/P(DLA-co-D-2H3MB) and P(L-2HB-co-L-2H3MB)/P(DLA-co-D-2H3MB) blends ranged from 149.3 to 163.6 °C, which were higher than the values observed for the unblended P(LLA-co-L-2HB) (84.8 and 88.7 °C) and P(L-2HB-co-L-2H3MB) (61.6–133.1 °C). This study shows the high SC crystallizability of the asymmetric combination of l- and d-configured chiral 2HAA-based random copolymers even when one of them was individually noncrystallizable. This result strongly suggests that SC crystallization occurred when the common monomer units were incorporated into both l- and d-configured 2HAA-based random copolymers. SC crystallization of new types of asymmetric combinations of l- and d-configured random copolymers is expected to diversify the attainable properties and biodegradation behavior of chiral 2HAA-based polymer materials.

Mombrú, Dominique; Romero, Mariano; Faccio, Ricardo; Mombrú, Álvaro W.

doi: 10.1038/s41428-022-00694-0pmid: N/A

Herein, we present a joint experimental and theoretical study using a multiscale computational simulation approach focusing on the roles of amorphous and crystalline regions in determining the optical and electronic properties of hybrid systems comprising poly(3-hexylthiophene) (P3HT) embedded with nitrogen- (N-GQDs) and nitrogen/sulfur-doped graphene quantum dots (NS-GQDs). The degree of crystallinity calculated with our experimental X-ray diffraction patterns is supported by our molecular dynamics calculations for the amorphous and crystalline models. Resonance and off-resonance Raman, UV‒Vis and impedance spectroscopy allowed us to demonstrate the enhancement in electronic charge transfer for both the amorphous and crystalline regions, particularly in the case of the P3HT:NS-GQDs. Our DFT calculations corroborate the presence of donor:acceptor interactions for the P3HT:NS-GQDs, while the opposite was observed for the P3HT:N-GQDs, in strong correlation with experimental data. Enhancing the knowledge of these fundamental aspects can be very useful for understanding the role of GQDs in polymeric solar cells and contributes to guiding their more rational design.

Nogami, Satoshi; Kadota, Kazunori; Uchiyama, Hiromasa; Arima-Osonoi, Hiroshi; Shibayama, Mitsuhiro; Tozuka, Yuichi

doi: 10.1038/s41428-022-00681-5pmid: N/A

In this study, the drug diffusion behavior and kinetics of gelatin hydrogels that were prepared with polymers were evaluated in terms of their rheological and rupture properties. The rheological and rupture properties of polymer-blended hydrogels prepared at pH 5.5 indicated that gelatin was homogeneously mixed with hydroxypropyl methylcellulose phthalate (HPMCP) or methacrylic acid-ethyl acrylate copolymer (Eudragit®) but not with hydroxypropyl methylcellulose or hydroxypropyl methylcellulose acetate succinate. We found that the release rate of nizatidine, a water-soluble drug, from the gelatin/HPMCP hydrogels might be inhibited compared with that from the gelatin/Eudragit® hydrogels at pH 1.2. This was because compared to the gelatin/Eudragit® hydrogels, the gelatin/HPMCP hydrogels had a higher crossover point between the strain-dependent storage and loss moduli. In addition, the gelatin/HPMCP and gelatin/Eudragit® hydrogels showed an increase in rupture stress and strain when the polymer content was increased. The drug diffusion mechanism of the gelatin/HPMCP hydrogel formulations from pH 1.0 to 6.0 was identified using four kinetic models. The findings indicated that the drug diffusion behavior of the gelatin/HPMCP gels below pH 2.0 was governed by diffusion of the drug. These results demonstrate that gelatin-based hydrogels with HPMCP are potential candidates for inhibiting the release of nizatidine in a gastric pH medium.

Hung, Yong-Tung; Chen, Chun-Kai; Lin, Yan-Cheng; Yu, Yang-Yen; Chen, Wen-Chang

doi: 10.1038/s41428-022-00696-ypmid: N/A

Biomass-based polymers featuring high thermal stability and low water absorption play a vital role in contributing to the environmental sustainability of flexible electronics. In this research, we developed a series of polyimides derived from (3 R,6 S)-hexahydrofuro[3,2-b]furan-3,6-diyl bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylate) (ISBESA), which can be synthesized from isosorbide bioresources. This study systematically analyzed the effect of ester or amide linkage presence and orientation on the performance of polyimides (PIs). The PI chain configuration and morphology were investigated via experimental results such as d-spacing or film density and theoretical calculations. After introducing the stiff ester linkage, PI-1 with a high chain coplanarity and stacking state exhibits a low water absorption of 0.34 and possesses outstanding thermal/mechanical stability, with a Tg higher than 300 °C, a CTE of 27.8 ppm K–1, and a Young’s modulus of 4.4 GPa, which is superior to those of most reported biopolymers and even Kapton® engineering plastics. In addition, PI-1 exhibits low dielectric properties, with a Dk of 2.84 and a Df of 0.004, due to the low chain polarity and dipole moment. We further demonstrate a flexible transistor based on PI-1 that shows electrical performance comparable to those of traditional silicon-based devices, even after thermal treatment at 150 °C or 1000 bending cycles.

Ishii, Satsuki; Akter, Mousumi; Murayama, Keiji; Kabir, Arif Md. Rashedul; Asanuma, Hiroyuki; Sada, Kazuki; Kakugo, Akira

doi: 10.1038/s41428-022-00693-1pmid: N/A

We report the swarming of microtubules driven by the biomolecular motor kinesin and dissociation of microtubule swarms under UV and visible light irradiation, respectively. We introduced para tert-butyl-substituted azobenzene, a photoresponsive molecule, to the backbone of single strand DNA, which functions as a photoswitch. Due to the photoswitch, the swarming of DNA-conjugated microtubules was controlled and reversible regulation of microtubule swarming was achieved in a repeated manner upon alternate irradiation with UV and visible light. This reversible swarming of microtubules could provide new opportunities for designing complex swarming systems with the ability of multitasking, expediting the development of molecular machines.