Triple Isomerism in 3D Covalent Organic Frameworks

Isomerism in covalent organic frameworks (COFs) has scarcely been known. Here, for the first time we show 3D COFs with three framework isomers or polymorphs constructed from the same building blocks. All isomers were obtained as large (>10 μm) crystals; although their crystal shapes were distinctly different, they showed identical FT-IR and solid-state NMR spectra. Our structural analyses revealed unprecedented triple isomerism in 3D COFs (noninterpenetrated dia, qtz, and 3-fold interpenetrated dia-c3 nets). Furthermore, this Communication reports the first known COF with qtz topology for which the structure determination was based on Rietveld analysis. We achieved triple framework isomerism by reticulating a tetrahedral building block with a flexible junction and a linear building block with PEO side chains and by varying solution compositions. Our energy calculations, along with the discovery of interisomer transition, revealed that the isomer with qtz topology was a kinetic isomer. Thus, this simple yet little-explored concept of reticulating only flexible building blocks is an effective pathway to significantly broaden the diversity of 3D COFs, which have been proposed for a myriad of applications.

Recent Advances in Biodegradable Polymers and Their Biological Applications: A Brief Review

The rising significance of the field of biopolymers has driven the rapid progress of this distinctive class of polymeric materials in the past decades. Biodegradable polymers have acquired much attention because they play an essential role in humans' lives due to their specific tunable electrical conductivity and biodegradability characteristics, making them fascinating in many applications. Herein, we debated the recent progress in developing biodegradable polymers and their applications. Initially, we introduce the basics of conducting and biodegradable polymers, trailed by debates about the effective strategies currently used to develop biopolymers. Special importance will focus on the uses of biodegradable polymers in drug delivery and tissue engineering, as well as wound healing, demonstrating the recent findings, and uses of several biodegradable polymers in modern biological uses. In this review, we have provided comprehensive viewpoints on the latest progress of the challenges and future prospects involving biodegradable polymers' advancement and commercial applications.

Polymersomes with asymmetric membranes and self-assembled superstructures using pentablock quintopolymers resolved by electron tomography

Polystyrene-block-poly(1,4-isoprene)-block-poly(dimethyl siloxane)-block-poly(tert-butyl methacrylate)-block-poly(2-vinyl pyridine), PS-b-PI-b-PDMS-b-PtBMA-b-P2VP, self-assembles in acetone into polymersomes with asymmetric (directional) PI-b-PDMS membranes.

Thermoresponse and self-assembly of an ABC star quarterpolymer with O2 and redox dual-responsive Y junctions

The stimuli-tunable LCST-type phase transition and self-assembly behaviors of a multi-responsive 3-miktoarm star bearing O₂/redox-sensitive and H-bond-switchable Y junctions were revealed.

Synthesis and self-assembly of a dual-responsive monocleavable ABCD star quaterpolymer

A modularly synthesized core-functionalized PEG-PSt-PCL-PAA miktoarm star can self-assemble into hollow nanocapsules that are sensitive to pH/redox stimuli and H-bond/polyion complexation.

CO2-Stimulated morphology transition of ABC miktoarm star terpolymer assemblies

CO₂-Regulated self-assembly of star terpolymers star-[poly(ethylene glycol)-polystyrene-poly[2-(N,N-diethylamino)ethyl methacrylate]] (μ-PEG-PS-PDEA) was studied and an unusual vesicle/microsphere-to-lamella transition upon CO₂ stimulation was observed.

Synthesis and properties of couplable ABCDE star copolymers by orthogonal CuAAC and Diels–Alder click reactions

Well-defined ABCDE star quintopolymers generated by a modular and orthogonal strategy could self-assemble into intriguing nanoobjects sensitive to thermal and pH stimuli.

Synthesis and pH-responsive self-assembly behavior of a fluorescent amphiphilic triblock copolymer mPEG-b-PCL-b-PDMAEMA-g-PC for the controlled intracellular delivery of doxorubicin

Schematic illustration of the pH-responsive self-assembly of a mPEG-b-PCL-b-PDMAEMA-g-PC copolymer with fluorescent coumarin units for controlling DOX release.

Bioinspired polymer vesicles and membranes for biological and medical applications

Biological membranes play an essential role in living organisms by providing stable and functional compartments, supporting signalling and selective transport. Combining synthetic polymer membranes with biological molecules promises to be an effective strategy to mimic the functions of cell membranes and apply them in artificial systems.

Synthesis and properties of an acid-labile dual-sensitive ABCD star quaterpolymer

Copolymer aggregates formed from an amphiphilic ABCD star could exhibit acid-induced topological and morphological transformations and stimuli-triggered drug delivery properties.

Synthesis of ABB′ and ABC star copolymers via a combination of NMRP and ROP reactions

Well-defined miktoarm star copolymers (ABB′ and ABC) were synthesized via a combination of NMRP and ROP using N-(2-hydroxyethyl)maleimide as the branching molecule.

Polymerization of Ethylene Oxide, Propylene Oxide, and Other Alkylene Oxides: Synthesis, Novel Polymer Architectures, and Bioconjugation

The review summarizes current trends and developments in the polymerization of alkylene oxides in the last two decades since 1995, with a particular focus on the most important epoxide monomers ethylene oxide (EO), propylene oxide (PO), and butylene oxide (BO). Classical synthetic pathways, i.e., anionic polymerization, coordination polymerization, and cationic polymerization of epoxides (oxiranes), are briefly reviewed. The main focus of the review lies on more recent and in some cases metal-free methods for epoxide polymerization, i.e., the activated monomer strategy, the use of organocatalysts, such as N-heterocyclic carbenes (NHCs) and N-heterocyclic olefins (NHOs) as well as phosphazene bases. In addition, the commercially relevant double-metal cyanide (DMC) catalyst systems are discussed. Besides the synthetic progress, new types of multifunctional linear PEG (mf-PEG) and PPO structures accessible by copolymerization of EO or PO with functional epoxide comonomers are presented as well as complex branched, hyperbranched, and dendrimer like polyethers. Amphiphilic block copolymers based on PEO and PPO (Poloxamers and Pluronics) and advances in the area of PEGylation as the most important bioconjugation strategy are also summarized. With the ever growing toolbox for epoxide polymerization, a "polyether universe" may be envisaged that in its structural diversity parallels the immense variety of structural options available for polymers based on vinyl monomers with a purely carbon-based backbone.

Synthesis of functional polyester for fabrication of nano-fibrous scaffolds and its effect on PC12 cells

An ideal scaffold should mimic the advantageous characteristics of a natural extracellular matrix for cell attachment, proliferation, and differentiation. In this study, well-defined block copolymer with functional groups was synthesized. The structure of the block copolymer was characterized by nuclear magnetic resonance, gel permeation chromatography, and differential scanning calorimetry. Thermally induced phase separation was employed to fabricate nano-fibrous scaffolds based on the synthesized block copolymer. The scaffold, with fiber diameter ranging from 400 to 500 nm, was fabricated for in vitro culture of PC12 cells. The carboxyl groups on the side chain resulted in increased hydrophilicity of nano-fibrous scaffolds and enhanced cell proliferation. In addition, this scaffold structure was beneficial in directing the growth of regenerating axons in nerve tissue engineering. Results of 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide (MTT) assay and scanning electron microscopy confirmed that the nano-fibrous scaffolds with functional groups were suitable for PC12 cells growth. Moreover, the carboxyl groups were suitable for coupling with biological signals. Thus, the nano-fibrous scaffolds have potential applications in tissue engineering.

Controlled release of anticancer drug Paclitaxel using nano-structured amphiphilic star-hyperbranched block copolymers

Two amphiphilic star-hyperbranched copolymers with different hydrophilic PHEMA segments were synthesized, and their drug loading/release profiles were examined by using Paclitaxel.

Cyclodextrin-tunable reversible self-assembly of a thermoresponsive Y-shaped polymer

The reversible self-assembly behavior of thermoresponsive γ-shaped polymer can be effectively tuned based on the inclusion complexation, intermolecular hydrogen bonding and steric hindrance of β-CD.