Nanoconfined Crosslinked Poly(ionic liquid)s with Unprecedented Selective Swelling Properties Obtained by Alkylation in Nanophase-Separated Poly(1-vinylimidazole)-l-poly(tetrahydrofuran) Conetworks

Dynamic Covalent Amphiphilic Polymer Conetworks Based on End-Linked Pluronic F108: Preparation, Characterization, and Evaluation as Matrices for Gel Polymer Electrolytes

We present the development of a platform of well-defined, dynamic covalent amphiphilic polymer conetworks (APCN) based on an α,ω-dibenzaldehyde end-functionalized linear amphiphilic poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol) (PEG-b-PPG-b-PEG, Pluronic) copolymer end-linked with a triacylhydrazide oligo(ethylene glycol) triarmed star cross-linker. The developed APCNs were characterized in terms of their rheological (increase in the storage modulus by a factor of 2 with increase in temperature from 10 to 50 °C), self-healing, self-assembling, and mechanical properties and evaluated as a matrix for gel polymer electrolytes (GPEs) in both the stretched and unstretched states. Our results show that water-loaded APCNs almost completely self-mend, self-organize at room temperature into a body-centered cubic structure with long-range order exhibiting an aggregation number of around 80, and display an exceptional room temperature stretchability of ∼2400%. Furthermore, ionic liquid-loaded APCNs could serve as gel polymer electrolytes (GPEs), displaying a substantial ion conductivity in the unstretched state, which was gradually reduced upon elongation up to a strain of 4, above which it gradually increased. Finally, it was found that recycled (dissolved and re-formed) ionic liquid-loaded APCNs could be reused as GPEs preserving 50-70% of their original ion conductivity.

Polyurethanes Modified by Ionic Liquids and Their Applications

Polyurethane (PU) refers to the polymer containing carbamate groups in its molecular structure, generally obtained by the reaction of isocyanate and alcohol. Because of its flexible formulation, diverse product forms, and excellent performance, it has been widely used in mechanical engineering, electronic equipment, biomedical applications, etc. Through physical or chemical methods, ionic groups are introduced into PU, which gives PU electrical conductivity, flame-retardant, and antistatic properties, thus expanding the application fields of PU, especially in flexible devices such as sensors, actuators, and functional membranes for batteries and gas absorption. In this review, we firstly introduced the characteristics of PU in chemical and microphase structures and their related physical and chemical performance. To improve the performance of PU, ionic liquids (ILs) were applied in the processing or synthesis of PU, resulting in a new type of PU called ionic PU. In the following part of this review, we mainly summarized the fabrication methods of IL-modified PUs via physical blending and the chemical copolymerization method. Then, we summarized the research progress of the applications for IL-modified PUs in different fields, including sensors, actuators, transistors, antistatic films, etc. Finally, we discussed the future development trends and challenges faced by IL-modified PUs.

Physical, Electrochemical, and Solvent Permeation Properties of Amphiphilic Conetwork Membranes Formed through Interlinking of Poly(vinylidene fluoride)-Graft-Poly[(2-dimethylamino)ethyl Methacrylate] with Telechelic Poly(ethylene glycol) and Small Molecular Weight Cross-Linkers

We report the preparation of dense and porous amphiphilic conetwork (APCN) membranes through the covalent interconnection of poly(vinylidene fluoride)-graft-poly[(2-dimethylamino)ethyl methacrylate] (PVDF-g-PDMAEMA) copolymers with telechelic poly(ethylene glycol) (PEG) or α,α-dichloro-p-xylene (XDC). The dense APCN membranes exhibit varying solvent swelling and mechanical properties depending on the compositions and overall crystallinity. The crystallinity of both PVDF (20-47%) and PEG (9-17%) is significantly suppressed in the dense APCNs prepared through the interconnection of PVDF-g-PDMAEMA with reactive PEG as compared to the APCN membranes (48-53%) prepared with XDC as well as mechanical blend of PVDF-g-PDMAEMA plus nonreactive PEG. The dense APCN membranes exhibit a good transport number of monovalent ions and ionic conductivity. The APCN membrane interconnected with PEG and containing binary ionic liquids exhibits a room-temperature lithium ion conductivity of 0.52 mS/cm. On the other hand, APCN ultrafiltration (UF) membranes exhibit organic solvent-resistant behavior. The UF membrane obtained by interconnecting PVDF-g-PDMAEMA with telechelic PEG shows low protein fouling propensity, higher hydrophilicity, and water flux as compared to membranes prepared using XDC as the interconnecting agent. The significant effect of the covalent interconnection of the amphiphilic graft copolymers with telechelic PEG or XDC on the overall properties provides a good opportunity to modulate the properties and performance of APCN membranes.

Synthesis and Structure of 2-Hydroxypropyl Methacrylate-Capped Isophorone Diisocyanate and Poly(Propylene Glycol) Urethane Mixtures and the Properties of their UV-Cured Co-Networks with Isobornyl Methacrylate

Polyurethane acrylate prepolymers with different contents of HIPIH and HIH were synthesized via reacting excessive isophorone diisocyanate (IPDI) with poly(propylene glycol) (PPG) and then end-capping with 2-hydroxypropyl methacrylate (HPMA) in isobornyl methacrylate (IBOMA). After the addition of the photoinitiator PI 1173, the resulting prepolymer resins were irradiated by UV light to form cured materials. The structures of the prepolymers were confirmed by ¹H NMR, FT-IR, and GPC. SEM analyses proved that no obvious phase separation was observed within the cured sample. As the content of HIH increased, the viscosity of the prepolymers increased slightly. In addition, the gel content, solvent resistance, Shore hardness, Young's modulus, and the tensile strength of the cured films increased, whereas the elongation at break decreased gradually. The volume shrinkage of the cured samples ranged between 4.5% and 4.8%. DMA analyses showed that the Tgs of the cured samples increased as more HIH structures existed. TGA analyses revealed that the cured samples had high thermal stability. This solvent-free fabrication process was simple, convenient, and controllable. By simply regulating the contents of HIPIH and HIH in the prepolymers, the performances of the cured materials could be adjusted to a wide range.

Stronger Together. Poly(Styrene) Gels Reinforced by Soft Gellan Gum

This study targets the synthesis of novel semi-interpenetrating networks and amphiphilic conetworks, where hydrophilic soft matter (Gellan Gum, GG) was combined with hydrophobic rigid poly(styrene), PSt. To achieve that, GG was chemically modified with 4-vinyl benzyl chloride to form a reactive macromonomer with multiple double bonds. These double bonds were used in a copolymerization with styrene to initially form semi-interpenetrating networks (SIPNs) where linear PSt was intertwined within the GG-PSt conetwork. The interpenetrating linear PSt and unreacted styrene were extracted over 3 consecutive days with yields 18–24%. After the extraction, the resulting conetworks (yields 76–82%) were able to swell both in organic and aqueous media. Thermo-mechanical tests (thermal gravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis) and rheology indicated that both SIPNs and conteworks had, in most cases, improved thermal and mechanical properties compared to pure poly(styrene) and pure GG gels. This crosslinking strategy proved that the reactive combination of a synthetic polymer and a bio-derived constituent would result in the formation of more sustainable materials with improved thermo-mechanical properties. The binding ability of the amphiphilic conetworks towards several organic dyes was high, showing that they could be used as potential materials in environmental clean-up.

Special Issue: Advanced Science and Technology of Polymer Matrix Nanomaterials

Nanotechnology has witnessed an incredible resonance and a substantial number of new applications in various areas during the past three decades [...]

Bottlebrush Amphiphilic Polymer Co-Networks

We report the synthesis of novel poly(ethylene glycol) and poly(dimethyl siloxane) (PEG and PDMS, respectively) bottlebrush amphiphilic polymer co-networks (B-APCNs) with high gel fractions by a grafting-through ring-opening metathesis polymerization. By varying the volume fraction of PEG (ϕPEG), we alter the crystallinity of the networks, achieving complete suppression of PEG crystallinity at ϕPEG=0.35. Furthermore, we show that the crystallinity of these networks can be tuned to alter their moduli. Through dynamic mechanical analysis, we show that the storage and loss moduli of networks with completely suppressed crystallinity (ϕPEG=0.35) behave similarly to a PDMS homopolymer bottlebrush network. These bottlebrush networks represent an unexplored architecture for the field of amphiphilic polymer co-networks.

Recent advances in poly(ionic liquid)s for biomedical application

Poly(ionic liquid)s (PILs) are polymers containing ions in their side-chain or backbone, and the designability and outstanding physicochemical properties of PILs have attracted widespread attention from researchers. PILs have specific characteristics, including negligible vapor pressure, high thermal and chemical stability, non-flammability, and self-assembly capabilities. PILs can be well combined with advanced analytical instruments and technology and have made outstanding contributions to the development of biomedicine aiding in the continuous advancement of science and technology. Here we reviewed the advances of PILs in the biomedical field in the past five years with a focus on applications in proteomics, drug delivery, and development. This paper aims to engage pharmaceutical and biomedical scientists to full understand PILs and accelerate the progress from laboratory research to industrialization.

Proton Exchange Membrane Fuel Cells (PEMFCs): Advances and Challenges

The study of the electrochemical catalyst conversion of renewable electricity and carbon oxides into chemical fuels attracts a great deal of attention by different researchers. The main role of this process is in mitigating the worldwide energy crisis through a closed technological carbon cycle, where chemical fuels, such as hydrogen, are stored and reconverted to electricity via electrochemical reaction processes in fuel cells. The scientific community focuses its efforts on the development of high-performance polymeric membranes together with nanomaterials with high catalytic activity and stability in order to reduce the platinum group metal applied as a cathode to build stacks of proton exchange membrane fuel cells (PEMFCs) to work at low and moderate temperatures. The design of new conductive membranes and nanoparticles (NPs) whose morphology directly affects their catalytic properties is of utmost importance. Nanoparticle morphologies, like cubes, octahedrons, icosahedrons, bipyramids, plates, and polyhedrons, among others, are widely studied for catalysis applications. The recent progress around the high catalytic activity has focused on the stabilizing agents and their potential impact on nanomaterial synthesis to induce changes in the morphology of NPs.

Modulation of Properties through Covalent Bond Induced Formation of Strong Ion Pairing between Polyelectrolytes in Injectable Conetwork Hydrogels

In situ simultaneous formation of both covalent linkages and ion pair is challenging yet necessary to control the biological properties of a hydrogel. We report that the generation of covalent linkages (⁺N-C) facilitates the simultaneous formation of ion pairs between polyelectrolytes (PEs) in a hydrogel network. Co-injection of tertiary amine functional macromolecules and reactive poly(ethylene glycol) (PEG) containing negatively charged PE leads to the formation of hydrogel conetworks consisting of covalent junctions and ion pairs. Our design is based on the gradual appearance of ⁺N-C junctions followed by formation of ion pairs. This strategy provides an easy access to hydrogel networks bearing a predetermined proportion of ion pair and covalent cross-linking junction. The proportion of ion pair could be varied by introducing a precalculated proportion of mono- and difunctional reactive PEG in the hydrogel system. The topology of the prepolymer and the hydrogel could be modulated (graft) during hydrogel formation. This approach is applicable to obtain covalent/ionic, covalent bond induced purely ionic, and purely covalent hydrogels of several macromolecular entities. The effect of ion pairing in the hydrogels is strongly reflected in the modulus, strain bearing, degradation, free volume, swelling, and drug release properties. The hydrogels exhibit microscopic recovery of modulus after application of high amplitude strain depending on the prepolymer concentration (chain entanglement) and nature of hydrogel network. The hydrogels are hemocompatible, and the covalent/ionic hydrogels show a slower release of methotrexate than that of the purely covalent hydrogel. This work provides an understanding for the in situ construction and manipulation of biological properties of hydrogels through the covalent bond induced formation of a strong ion pair.

The Scissors Effect in Action: The Fox-Flory Relationship between the Glass Transition Temperature of Crosslinked Poly(Methyl Methacrylate) and Mc in Nanophase Separated Poly(Methyl Methacrylate)-l-Polyisobutylene Conetworks

The glass transition temperature (Tg) is one of the most important properties of polymeric materials. In order to reveal whether the scissors effect, i.e., the Fox-Flory relationship between Tg and the average molecular weight between crosslinking points (Mc), reported only in one case for polymer conetworks so far, is more generally effective or valid only for a single case, a series of poly(methyl methacrylate)-l-polyisobutylene (PMMA-l-PIB) conetworks was prepared and investigated. Two Tgs were found for the conetworks by DSC. Fox-Flory type dependence between Tg and Mc of the PMMA component (Tg = Tg,∞ - K/Mc) was observed. The K constants for the PMMA homopolymer and for the PMMA in the conetworks were the same in the margin of error. AFM images indicated disordered bicontinuous, mutually nanoconfined morphology with average domain sizes of 5-20 nm, but the correlation between Tg and domain sizes was not found. These new results indicate that the macrocrosslinkers act like molecular scissors (scissors effect), and the Tg of PMMA depend exclusively on the Mc in the conetworks. Consequently, these findings mean that the scissors effect is presumably a general phenomenon in nanophase-separated polymer conetworks, and this finding could be utilized in designing, processing, and applications of these novel materials.