High Water Resistance and Enhanced Mechanical Properties of Bio-Based Waterborne Polyurethane Enabled by in-situ Construction of Interpenetrating Polymer Network

In this study,acrylic acid was used as a neutralizer to prepare bio-based WPU with an interpenetrating polymer network structure by thermally induced free radical emulsion polymerization.The effects of the content of acrylic acid on the properties of the resulting waterborne polyurethane-poly(acrylic acid)(WPU-PAA)dispersion and the films were systematically investigated.The results showed that the cross-linking density of the interpenetrating network polymers was increased and the interlocking structure of the soft and hard phase dislocations in the molecular segments of the double networks was tailored with increasing the content of acrylic acid,leading to enhancement of the mechanical properties and water resistance of WPU-PAA films.Notably,with the increase in content of acrylic acid,the tensile strength,Young’s modulus,and toughness of the WPU-PAA-110 film increased by 3 times,and 8 times,and 2.4 times compared with WPU-PAA-80,respectively.The WPU-PAA-100 film showed the best water resistance,and the water absorption rate at 96 h was only 3.27%.This work provided a new design scheme for constructing bio-based WPU materials with excellent properties.

Study of Hydrophobic Nature of Fullerene-Based Poly (Methyl Hydro Siloxane) and Polyacrylonitrile Interpenetrating Polymer Network

In this study, the effect of combining different molecular domains on single platform has been reported that revealed a proper packing and interpenetration of fullerene spheres with the monomeric species. The fabricated IPN system exhibits hydrophobic behavior in nature. An interpenetrating polymer network (IPN) of fullerene-based poly (methyl hydro siloxane) (PMHS) and polyacrylonitrile (PAN) was prepared. The synthesized polymer network was characterized using infrared (IR) spectroscopy, differential scanning calorimetric analysis (DSC), and scanning electron microscopic (SEM) technique. The IPN was analyzed by IR spectroscopy, which depicts presence of fullerene at 500 cm−1 and 1632 cm−1, presence of PHMS at 1050 cm−1, 1250 cm−1, 2225 cm−1, and 3000 cm−1 and presence of PAN at 3077 cm−1, 1299 cm−1, 1408 cm−1 and 2083 cm−1. Shifting in band positions indicated the interpenetration of the reacting species. DSC endotherm showed crystalline peak (Tc) at 117˚C, which indicated the crystalline nature of the synthesized IPN. The absence of Tg peak and clear observable Tc peak revealed crystalline behavior of polymeric network. The microstructure of the polymer network was observed by SEM technique, which revealed transparent and dual-phase morphology of the IPN surface. The fluorescent emission spectra of polymeric network were recorded on a spectrofluorometer which revealed fluorescent excitation and emission spectra of the IPN. The Emission spectra generated by radiative decay of excitations exhibit a maximal peak at 450 nm, suggesting that the synthesized IPN nanosheets were typically high-intensity blue light emitting materials. The FTIR investigations revealed multiple non-covalent interactions achieved by polymerization with physical anchoring on the polymeric network surfaces. Such interactions can be recognized as the driving force for the fabrication of hydrophobic flexible silicon-based materials with a self-cleansing action.

Studies on the Morphology of Natural Rubber/Polyacrylate Interpenetrating Polymer Networks

The interpenetrating polymer network(IPN) systems have attracted a lot of attention because of their unique two-phase structure and properties. There have been many publications concerning the IPNs in which poly (isoprene) (PIP) or polyacrylates (PAC) is formed as one of the networks.In the present study, Four serles of natural rubber(NR)/PAC IPNs were prepared and their morphologies were investigated with dynamic mechanics analysis(DMA) and transmission electron microscopy (TEM).

Preparation,Morphology and Damping Property of PU/UP Interpenetrating Polymer Networks

Interpenetrating polymer networks （IPNs） composed of acrylate-modified polyurethane （PU）/unsaturated polyester （UP） resin via simultaneous polymerization with various component ratios of PU/UP were prepared. The polymerization processes of IPNs were traced through infrared spectrum （IR） techniques, by which the phase separation in systems could be controlled effectively. Results for the morphology and miscibility among multiple phases of IPNs, obtained by transmission electron microscope （TEM） indicated that the domains between two phases were constricted in nanometer scales. The dynamic mechanical thermal analyzer （DMTA） detection results revealed that the loss factor （tanS） and loss modulus （E″） increased with the polyurethane amounts in system, and the peak value in curves of tanδ and E″ appeared toward low temperature ranges. Maximum tanδ values of all samples were above 0.3 in the nearly 50℃ ranges. Also, the mechanical properties of PU/UP IPNs were studied in detail.

Semi-Interpenetrating Novolac-Epoxy Thermoset Polymer Networks Derived from Plant Biomass

Bio-based phenol-formaldehyde polymer (BioNovolac) was developed by reacting molar excess of bio-oil/phenolwith formaldehyde in acidic medium. Glycidyl 3,5-diglycidoxybenzoate (GDGB), was prepared by directglycidylation of α-resorcylic acid (RA), a naturally occurring phenolic monomer. GDGB was crosslinked in thepresence of BioNovolac by anionic polymerization. Fourier transform infrared spectroscopy (FTIR) confirmedthe formation of semi-interpenetrating polymer networks. The glass transition temperature and moduli of biobasedcrosslinked systems were observed to increase with increasing GDGB content. Active chain density andmass retention measured by dynamic mechanical analysis (DMA) and Soxhlet extraction, respectively, indicated ahigh crosslink density of the cured networks. Scanning electron microscopy (SEM) images depicted thehomogeneity of the bulk phase. The preparation of bio-based epoxy-novolac thermoset network resulted inreduced consumption of petroleum-based chemicals.

Thermoreversible Thickening and Self-assembly Behaviors of pH/Temperature Dually Responsive Microgels with Interpenetrating Polymer Network Structure

The pH /temperature dually responsive microgels of interpenetrating polymer network( IPN) structure composed of poly( N-isopropylacrylamide)( PNIPAM) network and poly( acrylic acid)( PAA) network( PNIPAM /PAA IPN microgels) were synthesized by seed emulsion polymerization. The results obtained by dynamic laser light scattering( DLLS) show that the microgels have good pH /temperature dual sensitivities. The temperature sensitive component and the pH sensitive component inside the microgels have little interference with each other. The rheological properties of the concentrated PNIPAM /PAA IPN microgel dispersions as a function of temperature at pH 4. 0 or 7. 0 were investigated by viscometer,and the results displayed that only at pH 7. 0 the dispersions presented thermoreversible thickening behavior. Then the PNIPAM /PAA fibers were prepared by self-assembly of the PNIPAM /PAA IPN microgels in the ice-crystal templates formed by unidirectional liquid nitrogen freezing method. Field emission scanning electron microscopy( FESEM) images indicate that the PNIPAM /PAA fibers are rounded,randomly orientated and interweaved.

SYNTHESIS AND CHARACTERIZATION OF POLYDIMETHYLSILOXANE/POLYSTYRENE SEMIINTERPENETRATING POLYMER NETWORKS

The synthesis of pseudo- and semi-interpenetrating polymer networks (IPNs) based on polydimethylsiloxane (PDMS) and polystyrene (PS) is described. IPNs were obtained by simultaneous and in situ sequential synthesis procedure. The preliminary studies on IPNs properties such as transition temperature, microphase separation and mechanical behaviors have been carried out by using differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The experimental evidence clearly showed that semi-IPNs obtained by sequential synthesis procedure have higher interpenetrating extent than pseudo-IPNs synthesized by simultaneous procedure. Over the full composition, the PDMS/PS IPNs are immiscible. The pseudo-IPNs microphase separation can be greatly subdued through the formation of grafting bonds between two networks as well as the kinetic rate-matching of the individual network crosslinking.

Preparation of Semi-interpenetrating Polymer Network of Silicon Rubber and Poly(methyl methylacrylate) Using Supercritical CO_2

The heterogeneous free-radical polymerization of methyl methylacrylate (MMA) and divinylbenzene (DVB) as cross-linker within supercritical carbon dioxide-swollen silicon rubber (SR) has been studied as an approach to preparing semi-interpenetrating polymer network (semi-IPN) of SR and poly(methyl methylacrylate) (PMMA). The SR/PMMA semi-IPNs were characterized by scanning electron microscopy (SEM) and dynamic mechanical analyzer (DMA).

AN EPOXY/(METHYL METHACRYLATE)INTERPENETRATING POLYMER NETWORK FOR NONLINEAR OPTICS

An interpenetrating polymer networks (IPN) consisting of an epoxy-based polymer network and a polymethyl methacrylate network were synthesized and characterized. The IPN showed only one T-g, and hence a homogeneous-phase morphology was suggested. The second-order nonlinear optical coefficient (d(33)) of the IPN was measured to be 1.72 X 10(-7) esu. The study of NLO temporal stability at room temperature and elevated temperature (100 degrees C) indicated that the IPN exhibits a high stability in the dipole orientation due to the permanent entanglements of two component networks in the IPN system. Long-term stability of second harmonic coefficients was observed at room temperature for more than 1000 h.

Microstrueture and Properties of Fluoroelastomer/Butadiene-Acrylonitrile Rubber Interpenetrating Polymer Networks

Interpenetrating polymer networks （IPNs） based on fluoroelastomer/butadiene-acrylonitrile rubber （FKM/NBR） by molten blending at a high temperature and chemical cross-linking of two components were prepared. The influence of the two networks component on the mechanical properties and thermostabilities was studied. The experimental results show that the mechanical properties of the IPNs are superior to those of the individual FKM and NBR networks due to forming the case of interpenetrating and intercross-linking between the two networks, the mechanical properties and thermal resistance exhibit higher values when 80/20 （w/w） FKM and NBR is blended and respectively cured simultaneously. The co-continuous morphology of the IPNs in the blends of 80/20 （w/w） FKM/NBR is found by transmission electron microscopy （TEM）, the differential scanning calorimetry （DSC） determination shows that the blends of 80/20 （w/w） FKM/NBR have better compatibility, and the glass transition temperature of the elastomer is -21.5 ℃.

Effect of Polymer Network Morphology on the Performance of Polymer Dispersed Liquid Crystal (PDLC) Composite Films

The effects of the morphologies of liquid crystal (LC) droplets left in polymer network on the performance of polymer dispersed liquid crystal composite films were investigated.By adjusting the relative content range of the crosslinking and diluents,the morphologies of polymer network can be changed.Therefore,the properties of PDLC composite films with imparity polymer morphologies were obtained by experiments and the finite element simulation.Results of the experimental and finite element simulation showed that the electro-optical properties of PDLC composite films were inversely proportional to the domain size of the polymer network and the mechanical properties were proportional to the domain size of the polymer network.

Influence of Interpenetrating Polymer Networks (IPN) Microstructure on Underwater Acoustic Stealth Performance

According to the configuration and absorption theory of polymer macromolecule materials, a kind of IPN with wider temperature range and higher damping property was designed and synthesized. By using the spectrum of dynamic mechanical thermal analysis （DMTA） and acoustic pulse tube device, the microstructure, phase separation degree, phase size and phase continuity of IPN with different components were analyzed. The experimental results show that the nano size grade of phase, the continuous and homogeneous IPN phase can provide higher absorption coefficient. The absorption coefficient of optimized sample I09 is 0.7 in 2 kHz, and the absorption peak is 0.9 in 4 kHz. Then the underwater acoustic properties of modified IPN filled with mica, micro-balloon and nano-SiO2 were discussed respectively to indicate that the inhomogeneous property of filler-modified IPN can improve the underwater acoustic stealth performance effectively, and the micro size grade of these filler-modified IPN can work well in low frequency acoustic stealth.

Gas Permeability and Free Volume Hole Properties of Interpenetrating Polymer Network Studied by Positrons

A series of polyurethane/epoxy resin interpenetrating polymer networks （PU/ER IPN） were studied by positron annihilation lifetime spectroscopy （PALS）. The effects of epoxy resin type and content on the free volume properties in IPN were investigated. We found that in PU/ER IPN, the free volume hole size and fractional free volume showed a negative deviation due to closer segmental chain packing through some chemical bonding between PU and epoxy resin. Direct relationship between the gas permeability and the free volume has been established based on the free volume theory. Experimental results revealed that the free volume plays an important role in determining the gas diffusion and permeability.

Polymerization Process and Morphology of Polyurethane/Vinyl Ester Resin Interpenetrating Polymer Networks

有到 VER 的不同部件比率和 comonomers typesintroduced 的一系列聚氨酯( PU ) /vinyl 酉旨树脂( VER ) simultaneousIPNs (贯穿的聚合物网络)被综合，聚合进程被 Fourier transforminfrared 光谱学( FTIR )跟踪学习 IPN 和氢结合行动 withinmulti-component.Furthermore 的动力学，聚合的关系由词法信息 g 第一次详细与形态学处理

Topological Confinement in Reversibly Interlocked Polymer Networks

Recently, we reported a series of reversibly interlocked polymer networks(RILNs), whose mechanical robustness and functionalities improvement was believed to be derived from topological interlocking of two sub-networks, although the direct evidence for the deduction is still lacking. Herein, a specially-designed RILNs system, in which the inter-component hydrogen bonds can be shielded as needed, was prepared and used to study the micro-structures of RILNs, aiming to verify the existence of mechanical interlocking in RILNs. By changing the pH of the swelling solvent, the effect exerted by the inter-component non-covalent bonds was eliminated, so detailed information of the networks structure was exposed. The small angle X-ray scattering(SAXS) and small-angle neutron scattering(SANS) results indicated that swelling-induced structural evolution of the two sub-networks mutually affected each other, even when the inter-component hydrogen bonds were absent, proving the presence of topological interlocking. The findings may help to draw a more accurate physical image and reveal the detailed structureproperty relationship of RILNs.

A spatiotemporally-nonlocal continuum field theory of polymer networks

A physically-based continuum theory that captures the microstructure-dependent and temporal effects of both permanent and transient polymer networks is still lacking,despite the fact that it is greatly needed for the analysis of polymeric microstructures.To fill in this gap,this work proposes a physically-based spatiotemporally nonlocal continuum field theory.A general frame-work is established that quantitatively connects microscopic descriptions of polymer networks(chain energetics,chain-length distribution,assembly structure of the interpenetrating network,and rate of bond exchange reactions)to key components in the spatiotemporally nonlocal constitutive relations(explicit form of the nonlocal kernel function,magnitude of nonlocal characteris-tic length,two-phase weighting factors,and explicit form of the relaxation function),based on three hypotheses on the continuum viewpoint of the underlying discrete network structure:the existence of a finite bottom bound of volume to define intensive quan-tities,uniformity of energy density field inside the representative volume of a polymer network,and the condition for initiation of chain stretch.Applying the general framework to a permanent 8-chain concentric network yields a concrete two-phase nonlocal elasticity constitutive relation,where the explicit form of the kernel function can be derived by simply assuming an implicit form.Application to a transient network with bond exchange reactions yields a spatiotemporally nonlocal constitutive relation.The spatiotemporally nonlocal continuum theory can be helpful for exploring transformative and subversive high-performance materials involving the specific spatial stacking and arrangement of functional units through artificial design.

A topological polymer network with Cu(Ⅱ)-coordinated reversible imidazole-urea locked unit constructs an ultra-strong self-healing elastomer

It is exceedingly desired, but difficult to construct self-healing materials with both excellent mechanical properties and healing efficiency, which are usually realized by using mutually exclusive methods. Here, we reconcile this contradiction by utilizing copper-bis-(imidazole-2-yl)-methane-urea(Cu-BIMU) locked units based on novel designed dynamic imidazole-urea bonds with coupled multiple noncovalent bonds(coordination bonds, π-π stacking bonds, and hydrogen bonds). The coordination of Cu(II) greatly reduces the electron-cloud density of imidazole, which lowers the free energy barrier of imidazole-urea bonds and promotes their reversible dissociation, as demonstrated by the density functional theory and small-molecule model reaction. The topological design of Cu-BIMU polyurethane(Cu-BIMU-PU), which concentrates multiple crosslinking-in-one locked unit to avoid the formation of excessive crosslinking sites to ensure high chain mobility, facilitates self-healing. Accumulative extensive intermolecular interactions endowed excellent mechanical properties to the resulting Cu-BIMU-PU elastomer with a tensile strength of 65.3 MPa, among the highest ever-reported value. This work provides a novel molecular design principle for fabricating high-performance dynamic polymers.

A self-standing,UV-cured semi-interpenetrating polymer network reinforced composite gel electrolytes for dendrite-suppressing lithium ion batteries

A self-standing,flexible and lithium dendrite growth-suppressing composite gel polymer electrolyte membrane was designed for the use of room-temperature lithium ion batteries.The multi-functional composite semi-interpenetrating polymer network(referred to as“Cs-IPN”)electrolyte membrane was fabricated by combining a UV-cured ethoxylated trimethylolpropane triacrylate(ETPTA)macromer with alumina nanoparticles in the presence of liquid electrolyte and thermoplastic linear poly(ethylene oxide)(PEO).The polymer electrolyte membrane exhibits a semi-interpenetrating polymer network structure and a higher room temperature ionic conductivity,which impart the electrolyte with a significant cycling(120 mAh g^(-1)after 200 cycles)and a remarkable rate(137 mAh g^(-1)at 0.1℃,130 mAh g^(-1)at 0.5℃,119 mAh g^(-1)at 1℃ and 100 mAh g^(-1)at 2℃)performance in Li/LiFePO4 battery.More importantly,the polymer electrolyte possesses superior ability to inhibit the growth of lithium dendrites,which makes it promising for next generation lithium ion batteries.

Supramolecular Polymer Networks with Enhanced Mechanical Properties:The Marriage of Covalent Polymer and Metallacycle

Main observation and conclusion Supramolecular polymer networks(SPNs)have always been the focus of research due to their novel features of good processability,stimuli-responsiveness,self-healing,and recyclability.Herein,we report the preparation of a metallacycle-linked supramolecular gel via orthogonal metal-ligand interactions and host-guest interactions.A triangular metallacycle with three appended 21-crown-7(21C7)units was obtained by the metal coordination of nickel(II)-salen-based dipyridyl ligands and platinum(II)acceptors.The integration of this metallacycle and traditional copolymer bearing secondary ammonium salts constructed a SPN via host-guest recognition between 21C7 units and ammonium salts,and a supramolecular gel further formed at high concentration.Multiple stimulus responsiveness and self-healing properties of gel were observed.The gel exhibited better stretchability compared to relative gel formed by copolymer alone owing to the synergistic effect of covalent bonds and supramolecular interactions.Moreover,compared to the model gel without metallacycles,the gel showed higher storage and loss moduli,and exhibited stronger stiffness in the self-healing tests performed with rheometer,indicating the metallacycle played an important role in improving the stiffness and self-healing of the gel.Therefore,the feasible approach to the formation of SPNs by the marriage of covalent polymers and metallacycles is expected to open a new way to design novel SPNs.

Carbon dots confined in 3D polymer network: Producing robust room temperature phosphorescence with tunable lifetimes

Room temperature phosphorescence(RTP) is important in both organic electronics and encryption. Despite rapid advances, a universal approach to robust and tunable RTP materials based on amorphous polymers remains a formidable challenge. Here, we present a strategy that uses three-dimensional(3 D)confinement of carbon dots in a polymer network to achieve ultra-long lifetime phosphorescence. The RTP of the as-obtained materials was not quenched in different polar organic solvents and the lifetime of the RTP was easily tuned by adjusting the amount of crosslinking or varying the drying temperature of the 3 D molecular network. As a demonstration of potential application, as-obtained RTP materials were successfully used to prepare RTP fibres for flexible textiles. As well as bringing to light a fundamental principle for the construction of polymer materials with RTP, we have endowed traditional carbon dots and polymers with fresh features that will expand potential applications.