High-performance and robust high-temperature polymer electrolyte membranes with moderate microphase separation by implementation of terphenyl-based polymers

Acid loss and plasticization of phosphoric acid(PA)-doped high-temperature polymer electrolyte membranes(HT-PEMs)are critical limitations to their practical application in fuel cells.To overcome these barriers,poly(terphenyl piperidinium)s constructed from the m-and p-isomers of terphenyl were synthesized to regulate the microstructure of the membrane.Highly rigid p-terphenyl units prompt the formation of moderate PA aggregates,where the ion-pair interaction between piperidinium and biphosphate is reinforced,leading to a reduction in the plasticizing effect.As a result,there are trade-offs between the proton conductivity,mechanical strength,and PA retention of the membranes with varied m/p-isomer ratios.The designed PA-doped PTP-20m membrane exhibits superior ionic conductivity,good mechanical strength,and excellent PA retention over a wide range of temperature(80–160°C)as well as satisfactory resistance to harsh accelerated aging tests.As a result,the membrane presents a desirable combination of performance(1.462 W cm^(-2) under the H_(2)/O_(2)condition,which is 1.5 times higher than that of PBI-based membrane)and durability(300 h at 160°C and 0.2 A cm^(-2))in the fuel cell.The results of this study provide new insights that will guide molecular design from the perspective of microstructure to improve the performance and robustness of HT-PEMs.

Microphase Separation of Star-diblock Copolymer Films： a Dissipative Particle Dynamics Simulation

The microphase-separating behaviors of two types of star-diblock copolymers （Ax）4（By）4 and （A^Bg）4 in thin films are studied using the simulation technique of dissipative particle dynamics. A variety of ordered mesostructures have been observed and the simulated phase diagrams show obvious symmetries for the （Ax）4（By）a films and asymmetries for the （AxBy）4 films, besides, it is easier for the （Ax）4（By）4 than for the （A^By）4 to carry out microphase separation under the same conditions, which has been recognized in bulk and can be ascribed to the structural difference between the two types of star copolymers. There are some correspondences between the mesostructures formed in the film and those formed in bulk at the same composition fraction. Decreasing the thickness of film and strengthening the A-B repulsion both help the mesostructures enhance the degree of order. Composition fraction dependences of the mean-square radius of gyration in the two types of star copolymer films are almost contrary, which can be attributed to the differences in their respective structures. These findings can provide a guide to designing novel microstructures involving star-diblock copolymers via geometrical confinement.

Polymerization-induced microphase separation of polymer-polyoxometalate nanocomposites for anhydrous solid state electrolytes

Solid-state electrolytes(SSEs)with high ionic conductivity,mechanical stability,and high thermal stability,as well as the stringent requirement of application in high-temperature fuel cells and lithium-ion batteries is receiving increasing attention.Polymer nanocomposites(PNCs),combining the advantages of inorganic materials with those of polymeric materials,offer numerous opportunities for SSEs design.In this work,we report a facile and general one-pot approach based on polymerization-induced microphase separation(PIMS)to generate PNCs with bi-continuous microphases.This synthetic strategy transforms a homogeneous liquid precursor consisting of polyoxometalates(POMs,H_(3)PW_(12)O_(40),Li_(7)[V_(15)O_(36)(CO_(3))]),poly(ethylene glycol)(PEG)macro-chain-transfer agent,styrene and divinylbenzene monomers,into a robust and transparent monolith.The resulting POMs are uniformly dispersed in the PEG block(PEG/POM)to form a conducting pathway that successfully realizes the effective transfer of protons and lithium ions,while the highly cross-linked polystyrene domains(P(S-co-DVB))as mechanical support provide outstanding mechanical properties and thermal stability.As the POM loading ratio up to 35 wt%,the proton conductivity of nanocomposite reaches as high as 5.99×10^(-4) S/cm at 100℃ in anhydrous environment,which effectively promotes proton transfer under extreme environments.This study broadens the application of fuel cells and lithium-ion batteries in extreme environments.

EFFECT OF MOLECULAR WEIGHT AND FILM THICKNESS ON THE CRYSTALLIZATION AND MICROPHASE SEPARATION IN POLYSTYRENE-BLOCK-POLY(L-LACTIC ACID) THIN FILMS AT THE EARLY STAGE

We investigated the effects of molecular weight and film thickness on the crystallization and microphase separation in semicrystalline block copolymer polystyrene-block-poly（L-lactic acid） （PS-b-PLLA） thin films, at the early stage of film evolution （when Tg 〈 T 〈 TODT） by in situ hot stage atomic force microscopy. For PS-b-PLLA 1 copolymer which had lower molecular weight and higher PLLA fraction, diffusion-controlled break-out crystallization started easily. For PS-b-PLLA 2 with higher molecular weight, crystallization in nanometer scales occurs in local area. After melting of the two copolymer films, islands were observed at the film surface： PS-b-PLLA 1 film was in a disordered phase mixed state while PS-b-PLLA 2 film formed phase-separated lamellar structure paralleling to the substrate. Crystallization-melting and van der Waals forces drove the island formation in PS-b-PLLA 1 film. Film thickness affected the crystallization rate. Crystals grew very slowly in much thinner film of PS-b-PLLA 1 and remained almost unchanged at long time annealing. The incompatibility between PS and PLLA blocks drove the film fluctuation which subsequently evolved into spinodal-like morphology.

Synthesis and Microphase Separation Behavior of Random, Mixed Cylindrical Brush Copolymers Bearing Polystyrene and Poly(ε-caprolactone) Side Chains

A series of mixed, random cylindrical brush copolymers bearing polystyrene（PS） and poly（ε-caprolactone）（PCL） side chains were synthesized via the combination of ring-opening polymerization（ROP） and atom transfer radical polymerization（ATRP）. These novel cylindrical brush copolymers have been characterized by means of nuclear magnetic resonance（NMR） spectroscopy, gel permeation chromatography（GPC） and differential scanning calorimetry（DSC）. It was found that the mikto-armed cylindrical brush copolymers were microphase-separated in bulks and that the morphologies were dependent on the mass ratios of PS to PCL side chains. One of the cylindrical brush copolymers was employed to incorporate into epoxy thermoset to investigate effect of the mikto-armed cylindrical brush architecture on the reaction-induced microphase separation behavior. Depending on the concentration of the cylindrical brush in epoxy, the thermosets can display the morphologies with the spherical, worm-like and lamellar PS microdomains dispersing in continuous thermosetting matrices.

Flexible coatings with microphase separation structure attained by copolymers and ultra-fine nanoparticles for endurable antifouling

Incorporating antibacterial agent into biomimetic coating inspired by natural organisms with micronano structure surface has generated more interest for antifouling applications.In this work,poly(dimethylsiloxane)(PDMS)-based triblock copolymers and sub-20 nm nanoparticles Ag and heterogeneous Fe_(3)O_(4)-coated Ag(Fe_(3)O_(4)@Ag)were used to construct microphase separation topography with oriented copolymer blocks structure.The artificial surface was verified by atomic force microscopy and scanning electron microscopy images.Meanwhile,the surface exhibited relative stable hydrophobic property,which was demonstrated by the water contact angle and dynamic air-bubble contact angle measurements.Consequently,after immersed in BSA solution 24 h and 720 h,the actual BSA absorption amount of the surface with Fe_(3)O_(4)@Ag nanoparticles was as low as 10%and 27%that of the initial BSA amount,respectively.Moreover,the surface also showed remarkable antibacterial performance,which effectively suppressed the growth rate of Escherichia coli.The strategy of constructing the flexible micro p hase separation structure by introducing heterogeneous inorganic antibacterial nanoparticles into a block copolymer substrate opens up a new way to create an antifouling surface coating.

ORDERED STRUCTURAL EVOLUTION AND RELAXATION BEHAVIORS OF A SERIES MICROPHASE SEPARATED“HAIRY-ROD”POLYIMIDES WITH MULTIPLE ALKYL SIDE CHAINS

A series of“hairy-rod”polyimides,BBPA(n),with multiple alkyl side chains was prepared from 3,3',4,4'-biphenyltetracarboxylic dianhydride(BPDA)and 4,4'-biphenyldiamine substituted in the 2,2'-positions with benzoate,whichwas substituted in the 3,4,5-positions with ether side chains of varying lengths.The number of the methylene units,n,inthese alkyl side chains were in even numbers ranging from 8 to 18.Combining techniques of one-dimensional(1D)and 2Dwide angle x-ray diffraction,1D small angle X-ray scattering,differential scanning calorimetry experiments,it was found thatthis series of“hairy-rod”polyimides possess a micro-phase separation between the backbones and side chains.This led to theformation of ordered structures in two different length scales,of which both are hexagonal packing:one is attributed to thealkyl side chains on the sub-nanometer scale,and another is for the whole polymer chains on the nanometer scale.Thedevelopment of the hexagonal structure on the sub-nanometer scale was critically dependent upon the lengths of the alkylside chains.Three relaxation processes were captured by dynamic mechanical analysis,i.e.,segmental motion of thebackbones,α,the melting of the side chain crystals,β_1,which exits only for the materials with longer side chains(n=18,16);and the subglass relaxation of side chains,β_2.The peak relaxation temperature of the α process decreased withincreasing the length of side chains,while the one of the β_2 process increased.The activation energy of the α relaxation wasrelatively independent on the length of side chain,whereas,β_2 process showed the increasing of activation energy withincreasing the length of side chains.

SYNTHESIS AND CHARACTERIZATION OF AMPHIPHILIC GRAFT COPOLYMER CONTAINING MICROPHASE SEPARATED AND LONG POLY(ETHYLENE OXIDE) SIDE CHAIN STRUCTURES

Acryloyl terminated Poly (ethyleneoxide)macromonomers (PEO-A) with different PEO chain lengths have been prepared by deactivation of PEO alkoxide with acryloyl chloride. A new kind of amphiphilic polystyrene-g-poly (ethylene oxide)graft copolymer containing both microphase separated and PEO side chain structures has been synthesized from radical copolymerization of PEO-A macromonomer with styrene. After careful purification by a newly-developed method called 'selective dissolution', the well-defined structure of the purified copolymers was confirmed by IR, ~1H-NMR and GPC. Various experimental parameters controlling the copolymerization were studied in detail. The results indicated that the feed ratio of styrene to macromonomer(S/M) was the most important determining factor for the composition of the copolymers. A detailed 'comb- model' was proposed to describe the molecular structure of the graft copolymers. Finally, this amphiphilic graft copolymers may readily form microphase separated structures as clearly indicated by transmission electron microscopy.

MICROPHASE SEPARATED STRUCTURES AND PROPERTIES OF PDMS-MDIPEG COPOLYMER SURFACE

A series of poly(dimethylsiloxane)(PDMS)-4,4′-diphenylmethanediisocyanate(MDI)-poly(ethylene glycol)(PEG) multiblock copolymers were synthesized by employing two-step growth polymerization and investigated by AFM,XPS. contact angle system,protein adsorption and platelets adhesion measurements,respectively.It was found that as the molecular weight of PDMS increased,the surface of copolymers had increasing phase separation,while the increase in the molecular weight of PEG decreased the phase separation extents of the copolymer surface.XPS and contact angle measurements showed that the greater the phase separation extent was,the lower both the surface enrichment of PDMS and the surface free energy of the copolymer film were.The protein adsorption experiments indicated that the best phase separation did not exhibit the best biocompatibility.

Synthesis, Purification and Characterization of Amphiphilic and Microphase Separated Graft Copolymer Polystyrene-g-Poly(ethylene oxide)

The present paper covers the poly (ethylene oxide) macromer with vinyl benzyl terminal group (PEO-VB) prepared by deactivation of the alkoxide function of mono-functional 'living' PEO chains with vinyl benzyl chloride (VBC). The obtained macromers were subjected to careful purification and detailed characterization. A new kind of amphiphilic polystyrene-g-poly(ethylene oxide) (PS-g-PEO) with both mi-crophase separated and PEO side chains was synthesized from radical copolymerization of PEO-VB macromer with styrene monomer. An improved purification method, referred as 'selective dissolvation', was established for the isolation of graft copolymers from the grafting products, and the purity and yield of the purified copolymers were satisfactory. The well-defined structure of the purified copolymers was confirmed by IR, 1H NMR and GPC. The bulk composition of the graft copolymers was determined by a well-established first derivative UV spectrometry. Various experimental parameters controlling the copolymerization were also studied. The results indicate that the feed ratio of macromer to styrene (M/S) was the most important factor in determining the composition of the copolymers. Thus a series of PS-g-PEO with a wide range of bulk compositions were obtained simply by adjusting the value of M/S. As clearly indicated by transmission electron microscopy, this amphiphilic graft copolymers may readily form microphase separated structures.

Influence of Diisocyanate on Polyurethane Elastomers Which Crosslinked by β-Cyclodextrin

A series of polyurethane elastomers (PUEs) were synthesized by using β-cyclodextrin (β-CD) as cross-linker from aliphatic, alicyclic, aromatic diisocyanates, and polyol. The PUEs were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), swelling test, hardness test and tensile test. The influence of diisocyanate on microphase separation and properties of PUEs was evaluated.

Nanoindentation Measurements of Mechanical Properties of Polyurethane Elastomers Which Crosslinked by β-Cyclodextrin

A series of PUEs which use β-CD as cross-linker were synthesized. Nanoindentation measurements of mechanical properties of these PUEs were made. Load and depth sensing indentation and nano DMA mode were used to evaluate mechanical properties of PUEs in nano-scale. The difference between the results from two modes proved the microphase separation in PUEs and to investigate PUE from hard domains and soft domains was of great significance.

Designing Tough,Printable,and Adaptable Eutectogels with Multinetworks via Synergy of Rapid Orthogonal Photopolymerizations and Solvent Effect in Seconds

Achieving a straightforward design of tough,printable,and adaptable polymeric eutectogels is still challenging in related fields due to the uncontrollable polymerization and solvent-exchanging processes,and inherent contrasting multiple networks.Here,we report a one-step synergistic strategy based on ruthenium chemistry-catalyzed photopolymerization and solvent effect for preparing high-performance eutectogels.This orthogonal ruthenium photochemistry helps multinetworks formation via phenol-coupling of gelatin and copolymerization of acrylamide(AAm)and[2-(methacryloyloxy)ethyl]trimethylammonium tetrafluoroborate(META)monomers in seconds.The obvious difference in the supramolecular interactions of free AAm monomers and polymerized units in P(AAm-co-META)with deep eutectic solvents(DESs)significantly promotes the microphase-separation behavior in eutectogels.Consequently,the in situ polymerization and microphase-separation behavior enable the as-prepared eutectogel materials to have excellent mechanical properties(stress of∼1.2 MPa),toughness(∼4.0 MJ m^(−3)),elasticity,adaptivity,and conductivity(∼0.5 S m^(−1)at room temperature).Also,the critical strength of the resultant eutectogels can be modulated by varying the DES constituents.This rapid and well-controlled synergistic approach is compatible with extrusion printing techniques to make flexible sensors with high sensitivities and response times to detect pressure in a range of 0–500 kPa.Such a general and simple strategy has application potential in biological,engineering,and material sciences.

Solvent‑aided phase separation in hydrogel towards significantly enhanced mechanoresponsive strength

Understanding working principles and thermodynamics behind phase separations,which have significant influences on condensed molecular structures and their performances,can inspire to design and fabricate anomalously and desirably mechanoresponsive hydrogels.However,a combination of techniques from physicochemistry and mechanics has yet been established for the phase separation in hydrogels.In this study,a thermodynamic model is firstly formulated to describe solvent-aided phase and microphase separations in the hydrogels,which present significantly improved mechanoresponsive strengths.Flory-Huggins theory and interfacial energy equation have further been applied to model the thermodynamics of concentration-dependent and temperature-dependent phase separations.An intricately detailed phase map has finally been formulated to explore the working principle.The thermodynamic methodology of phase separations,combined with the constitutive stress-strain relationships,has a great potential to explore the working mechanisms in mechanoresponsive hydrogels.

Self-assembly Promoted Crystallization of Diblock Copolypeptoids in Solution

Comprehensive Summary,Great efforts have been lately devoted to fabricating well-defined nanostructures using crystallization-driven self-assembly(CDSA)strategy.The influence of self-assembly on crystallization is also of great interest.Here,a series of amphiphilic diblock copolypeptoids poly(N-allylglycine)-b-poly(N-octylglycine)modified with cysteamine hydrochloride((PNAG-g-NH_(2))-b-PNOG)were synthesized by ring-opening polymerization(ROP)and post-polymerization functionalization.The diblock copolypeptoid is comprised of one hydrophobic crystalline PNOG block and one hydrophilic amorphous block,which can aggregate into nanostructured assemblies with soluble PNAG-g-NH_(2) as the corona layer and PNOG as the inner core in aqueous solution.With a systematic study by differential scanning calorimetry(DSC)and wide-angle X-ray scattering(WAXS),we demonstrated that the self-assembly of the block copolymers strengthens the crystallization of the PNOG block.

Macroscopic Regulation of Hierarchical Nanostructures in Liquid-crystalline Block Copolymers towards Functional Materials

The great potential of liquid-crystalline block copolymers(LCBCs)containing photoresponsive mesogens toward novel applications in photonics and nanotechnology has been attracting increasing attention,due to the combination of the inherent property of microphase separation of block copolymers and the hierarchically-assembled structures of liquid-crystalline polymers(LCPs).The periodically ordered nanostructures in bulk film of LCBCs can be acquired by supramolecular cooperative motion,derived from the interaction between liquid-crystalline elastic deformation and microphase separation,which are able to improve physical properties of polymer film toward advanced functional applications.Moreover,various micro/nano-patterned structures have been fabricated via light manipulation of photoresponsive LCBCs with good reproducibility and mass production.Thanks to recent developments in synthesis and polymerization techniques,diverse azobenzene-containing LCBCs have been designed,resulting in the creation of a wide variety of novel functions.This review illustrates recent progresses in macroscopic regulation of hierarchical nanostructures in LCBCs towards functional materials.The existing challenges are also discussed,showing perspectives for future studies.

Thermal properties of polyurethane elastomer with different flexible molecular chain based on para-phenylene diisocyanate

This work focuses on the relationship between flexibility of molecular chains and thermal properties of polyurethane elastomer（PUE）, which laid the foundation of further research about how to improve thermal properties of PUE. A series of PUE samples with different flexibility of molecular chains was prepared by using 1,4-butanediol（1,4-BDO）/bisphenol-a（BPA） blends with different mole ratios including9/1, 8/2, 7/3, 6/4 and 5/5. As comparison, PUE extended with pure 1,4-BDO and BPA was also synthesized.These samples were characterized by differential scanning calorimetry（DSC）, thermogravimetric analysis（TGA）, dynamic mechanical analysis（DMA）, etc. The results showed that with the decrease in flexibility of molecular chains the glass transition temperature（Tg） increased and low-temperature properties became worse. Besides, all samples had a certain degree of microphase separation, and soft segments in some samples were crystallized, i.e. the decreasing flexibility of molecular chains led to the impossibility of chains tightly packing and crystalline domains forming so that the degree of microphase separation decreased and the thermal properties became worse.

Double-Cable Conjugated Polymers with Fullerene Pendant for Single-Component Organic Solar Cells

In this work,the“functionalization-polymerization”(FP)method has been used to construct fullerene-contained double-cable conjugated polymers with“donor-acceptor”backbones.It was realized via synthesizing a fullerene-contained monomer and performing Stille polymerization.With this method,a series of double-cable conjugated polymers with different fullerene contents were developed and applied into single-component organic solar cells.The power conversion efficiencies(PCEs)based on these polymers increased from 0.71%to 1.71%with the enhanced fullerene contents.The relatively low PCEs might be originated from the poor microstructure in these polymers.These new conjugated polymers with molecular heterojunction would show potential application in organic electronic devices.

Preparation of porous polyimide microspheres by thermal degradation of block copolymers

A new preparation method has been developed for thermally stable porous polyimide microspheres. Porous polyimide microspheres were prepared using trib]ock copolymers that consisted of a thermally stable polyimide derived from pyromellitic dianhydride/4,4＇-oxydianiline as the continuous phase and a thermally labile polyether as the dispersed phase. Spheres of copolymers were generated in a nonaqueous emulsion and then gradually heated to complete the imidization to form a microphase-separated structure. Subsequently, thermal treatment at a slightly reduced pressure removed the labile blocks and produced pores. Under suitable decomposition conditions, the pore size of the porous polyimide was in the range of 200-400nm.

Modeling of specific structure crystallization coupling with dissolution

In this paper,the research framework for specific structure crystallization modeling has been proposed in which four steps are required in order to investigate the rigorous crystallization modeling by thermodynamics.The first is the activity coefficient model of the solution,the second is Solid-Liquid equilibrium,the third and fourth are the dissolution and crystallization kinetics modeling,respectively.Our investigations show that the mechanisms of complex structure formation and microphase transition can be analyzed by combining the dissolution and crystallization kinetics modeling.Moreover,the formation mechanism of the porous KCl has been analyzed,which may provide a reference for the porous structure formation in the advanced material synthesis.