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Strain sensors with high sensitivity, long-term durability, and stretchability are required for flexible and wearable electronic devices. This paper reports a bilayer strain sensor consisting of carboxyl-functionalized carbon nanotubes (CNTs) and ionically crosslinked polysiloxane substrates based on unsaturated acid-amine interactions. Vacuum filtration was adopted to prepare the CNT films (2.74-4.70 μm in thickness) onto the polysiloxane substrates to prepare stretchable conductive strain sensors. The strain sensor exhibited self-healing ability, self-adhesiveness, high sensitivity, linearity, low hysteresis, and long-term durability with a gauge factor of 33.99 at 55% strain. The sensitivity and linearity could be adjusted by the thickness of the CNT layer. A crack-related mechanism was proposed in which increasing the thickness of the CNT layer led to simultaneously enhanced sensitivity and linearity. Finally, we investigated the detection of human activities (bending/unbending of fingers or knees) and subtle motions (coughing and swallowing). The fabricated strain sensor succeeded in meeting various needs with satisfactory sensing performance.

Treatment of chronic wounds, such as diabetic feet, pressure sores and skin ulcer, has been a difficult issue for wound dressings. It is of great interest but challenging to develop an ideal dressing for chronic wounds with long-term functionality, transparency for clinical observation and adaptability to skin deformation. In this work, we designed a supramolecular polydimethylsiloxane (PDMS) elastomer material with double layer structure. After a series characterizations including mechanical properties, adhesion properties, water-vapor permeability and bio-compatibility, this bi-layer film (BLF) is evaluated as a wound dressing in the wound healing model in both normal and diabetic rat. The results show that the BLF dressing has good bio-compatibility, similar moisture permeability and adhesion properties compared with a commercial medical Tegaderm™ film. Moreover, benefiting from the comparatively lower modulus, the BLF dressing provides more stable attachment to the skin and an enclosed moist healing environment for the wounds, which is found to promote the healing process in the early stage.

Polymer blending has always been a critical strategy for preparing high-performance materials. By creating an interpenetrating polymer network (IPN), the incompatibility of different polymers could be overcome and a favorable bicontinuous phase structure could be achieved. Recently, the concept of covalent adaptable networks (CANs) based on reversible covalent bonds has brought many opportunities for developing and engineering sustainable high-performance polymer blends. Herein, we utilized the reversible hydrolysis/condensation of imines and boronic-esters to construct an interpenetrating covalent adaptable network (IPCAN) with a highly uniform phase structure from two immiscible single CANs, and to establish a closed loop between recycling single networks and regenerating IPCANs as well. The resultant IPCANs show not only a remarkable improvement in mechanical performance, but also a high restoration efficiency during multiple reprocessing. The outcomes of this work may provide new ideas for developing more sustainable high-performance polymer blends and IPNs with covalent reversible bonds.

Zwitterionic polymers have been used to cope with nonspecific protein adsorption and bio-fouling problems for a wide range of materials, including biomedical devices, marine coatings and membrane separation. However, direct surface modification with highly water-soluble zwitterionic polymers is rather difficult due to their poor attachment to hydrophobic solid surfaces. In this work, we utilize the hydrophobic interaction to anchor zwitterionic polysiloxanes grafted with cysteine onto surfaces by adding an hydrophobic block of polydimethylsiloxanes, referred as PDMS-b-(PDMS-g-Cys)s. The synthesis involves only three steps of reactions, and the structures of each product were characterized using GPC, FT-IR and 1H NMR. The adsorption and protein resistance of PDMS-b-(PDMS-g-Cys)s on a gold surface are investigated with QCM-D. The results show that the hydrophobic interaction moieties of the additional PDMS blocks help the hydrophilic cysteine-grafted blocks stably attach and then function on the sensor. These findings suggest that the addition of hydrophobic moieties provides an effective approach to construct anti-fouling interfaces with zwitterionic polymers in aqueous solution.

The rapid expansion of dynamic covalent chemistry world urges for materials not only possessing high mechanical properties and stretchability, but also including high reprocessability and reforming. Herein, aromatic disulfide-containing polysiloxanes elastomers with modified urea as chain-extender and crosslinker were first designed and fabricated. Dynamic crosslinks, including hydrogen bonding formed between urea and amide bonds, and aromatic disulfide are connected with polysiloxanes backbones through isocyanate (DTSA-HDI) reacted with systematically controlled aminopropyl groups in the side chains. Consequently, a series of ATPx-SS elastomers with polysiloxanes of different molecular weight and APPx-SS elastomers with different crosslinking densities are developed. The molar amount of DTSA-HDI has been proved to play a crucial role in adjusting the mechanical and thermal properties of the networks. Among all, ATP3-SS showed the best stretchability, of which the elongation at break was as high as 780%. APP1-SS achieved the highest tensile strength of 2.60 MPa. Besides, it has outstanding reprocessability and can be reprocessed and reformed without much decline of tensile strength after several cycles of hot-pressing. These remarkable properties demonstrate that the aromatic disulfide-containing elastomers are competitive to those un-filled polysiloxanes elastomers based on dynamic bonds ever reported.

Dual-crosslinked supramolecular elastomers with the hybrid network consisting of hydrogen bonds and covalent bonds combine the reversibility of hydrogen bond and mechanical properties of covalent crosslinking network. In this article, isocyanate mixture is used as curing agent to prepare dual-crosslinked elastomer based on bifunctional polydimethylsiloxane under mild condition. This method can effectively build up a hybrid network with the designed structure. A series of elastomers with same hydrogen bond density and variable covalent crosslinking degree are obtained. Swelling measurements and 1H-NMR spectra confirm the feasibility and controllability of curing method, the increasing of bifunctional isocyanate give rise to higher covalent crosslinking degree, improving the solvent resistance. The studies on viscoelastic property show that the introduction of an irreversible covalent crosslinking network stabilize the hybrid network, restrain the chain movement. The mechanical and self-healing property studies reveal that the covalent crosslink significantly reinforce the whole network, while the reparable strength seems to mainly depend on the hydrogen bond density. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016.

Covalent adaptive networks have shown great potential in sustainable crosslinked polymer materials. The incorporation of reversible covalent bonds also brings many possibilities for the material processing and recycling. Herein, we designed a polydioxaborolane network (PDOB) with abundant boronic-ester linkages. PDOBs showed tunable mechanical properties and viscoelasticity from highly stretchable elastomer to rigid thermoset by varying the composition. The dynamic dioxaborolane metathesis and reversible hydrolysis/rebinding of boronic-esters endowed PDOBs with remarkable reprocessability with the assistance of heat or moisture. Furthermore, the theoretical topology freezing transition temperature (Tv) of PDOBs was calculated to be below their glass transition temperature (Tg). We investigated the reprocessability of PDOBs at different temperature and found that PDOBs could be remolded at a temperature window between Tv and Tg even without the participation of water. The compressive force could break the reversible linkages into reactive sites, as well as promote exchange reactions, which subsequently facilitated interfacial integration.

Polydimethylsiloxanes (PDMS) are soft materials with high elasticity and excellent biocompatibility, giving them high potential for widespread applications as biomaterials. However, the application of PDMS to wound dressing is limited due to its shortcomings, particularly its non-absorptive and poor adhesive properties. This work addresses these limitations in two ways: first, a hydrophilic and biocompatible polyethylene glycol (PEG) block was introduced to the PDMS main chain to obtain carboxyl acid terminated PDMS-b-PEG-b-PDMS copolymers (EPMDS–COOH2); second, EPMDS–COOH2 polymers were reacted with diethylenetriamine and urea via a two-stage route to obtain a novel supramolecular elastomer (ESESi) based on multiple hydrogen bond association. Compared with the supramolecular elastomer based on simple PDMS (SESi), the hydrophilicity, water-absorption rate, adhesive ability and rate of water vapor permeation were significantly improved, enhancing the properties of ESESi films for application to wound dressing. After fully evaluating the bio-compatibilities of ESESi films, a full-thickness dermal wound model was chosen to estimate the healing performance, and traditional vaseline gauze, SESi film and commercialized Tegaderm™ film were chosen as controls. The results confirmed that the ESESi polymer could promote the healing of a skin wound to some extent, mainly due to its improved absorption and adhesive properties.

An improved process was developed for the production of carbon black (CB)–filled styrene butadiene rubber masterbatch (SBR-CB-MB) using a simple latex/CB mixing technology; the improvement comprised processing the CB as an emulsifier-free aqueous suspension by high-rate shearing. Tensile and tear strength, dynamic compression behaviors, the Payne effect, equilibrium swelling and bound rubber of the SBR-CB-MB and dry mixing CB filled SBR (SBR-CB-DM), covering a wide range of CB loading (45–70 phr), were investigated and compared. It was found that the tensile and tear strength, heat buildup and compression set, abrasion volume loss, and the Payne effect of the SBR-CB-MB were lower than those of the SBR-CB-DM, while the bound rubber content were higher, indicating good CB/rubber interaction in the SBR-CB-MB. SEM analysis showed that no free CB could be found on the surface or inside of the granular SBR-CB-MB particles, indicating good CB dispersion in the rubber matrix.

Polydimethylsiloxane (PDMS) is a widely used material for biomedical applications. In this work, a convenient method for the covalent modification of PDMS with carboxybetaine was developed and used to construct a biocompatible and anti-fouling coating. Following the preparation of a Si–H functionalized PDMS film by adjusting the molar ratio of the two components used in Sylgard 184 silicone elastomer networks, the allyl carboxybetaine (ACB) was grafted to the PDMS surface via a hydrosilylation reaction in the presence of a Karstedt's catalyst. ATR-FTIR and water contact angle measurements revealed that carboxybetaine was introduced to the PDMS surface successfully. The biocompatibilities of PDMS and carboxybetaine-modified PDMS (PDMS-CB) films were evaluated by cytotoxicity, hemocompatibility, and dynamic clotting time. The anti-fouling properties of PDMS-CB were evaluated by protein adsorption and bacterial adhesion measurements. The results showed that the carboxybetaine layer could enhance the biocompatibility of PDMS and reduce the adsorption of protein and adhesion of bacteria efficiently.

Reversible covalent bonds have been comprehensively reported to endow traditional crosslinked elastomers with reprocessability and recyclability. Herein, we prepared a polyimine elastomer (PIE) with abundant dynamic reversible imine bonds from small-molecular aldehydes and amines. More interestingly, we observed an unusual stress intensification phenomenon under constant strain during the typical tensile stress relaxation tests on PIEs. Reversible imine chemistry was revealed to control the stress relaxation and intensification, as well as to facilitate the restoration of network integrity. This unusual phenomenon reflects that structural reconfiguration is proceeding in dynamic reversible networks during deformation and determining the materials’ mechanical response to external deformation.

Boron-containing compounds are often used to construct networks in various research fields and industrial applications. Although borate-crosslinked poly(vinyl alcohol) (PVA) hydrogels and famous toy-product slime have achieved success in the market, there is still a lack of alignment between this success and the understanding of the structure of borate-hydroxyl complexes. Elastomers based on borate-hydroxyl complexes have not yet gained enough attention due to their poor mechanical properties. In this study, hydroxyl-modified polysiloxanes (HS-X) of four different grafting degrees was simply crosslinked by sodium tetraborate (SB) to prepare a novel polydimethylsiloxane (PDMS) elastomer based on borate-hydroxyl complex. The final products showed excellent thermodynamic stability over the tested temperature range. By simply changing the input amount of borate, the rheological and mechanical properties of the elastomers varied widely. Hot-pressing has been proven to be an efficient way to recycle the products and did not cause any decrease in the mechanical properties. Inspired by two common products, slime and PVA hydrogel, the present study was able to reproduce the previous success of borate-hydroxyl complexes to polysiloxanes system. It also provided a new approach for the preparation of novel elastomers based on dynamic reversible covalent bonds.

Suspension graft copolymerization of methyl methacrylate and acrylonitrile onto ethylene–propylene–diene terpolymer (EPDM) was carried out under different reaction conditions. A series of graft products of EPDM-graft-methyl methacrylate and acrylonitrile (EPDM-g-MAN), characterized by Fourier-transform infrared spectroscopy, was blended separately with styrene–acrylonitrile (SAN) resin to investigate their toughening effect on SAN matrix. The relationship between the polarity of EPDM-g-MAN and toughness of EPDM-g-MAN/SAN resin blends (AEMS) was evaluated. The compatibility and morphologies of AEMS were probed by dynamic mechanical analysis, transmission electron microscopy, and scanning electron microscopy to determine the toughing mechanism of the blends. Thermogravimetry results showed that the thermal stability of AEMS was enhanced with the incorporation of EPDM-g-MAN graft copolymer.

A series of hydrogen terminated polydimethylsiloxanes (PDMS-H) had been controlled synthesized via ring-opening polymerization. Then, methylmethacrylate (MMA) and tert-butyl methacrylate (tBMA) were grafted to PDMS-H via hydrosilylation reactions in the presence of Speier's catalyst, the hydrosilylation addition patterns of MMA and tBMA showed a strong preference toward β-1,2 addition, no α-1,2 addition product or 1,4-addition product was observed. Carboxyl terminated polydimethylsiloxanes were prepared by subsequent hydrolysis reaction in an aqueous NaOH/ethanol solution and under acid condition, respectively. Both methods could obtain carboxyl terminated polydimethylsiloxanes successfully. However, a significant decrease of the molecular weight of products was observed in the alkaline hydrolysis process, while the acid hydrolysis of tertiary butyl ester group terminated polydimethylsiloxanes could be conducted in a highly controlled manner. Besides, the synthesis of carboxyl terminated polydimethylsilox...

Using the characteristics of silica sol dispersing well in water and easy formation of silica gel when the silica sol is heated, by mixing a system of concentrated natural rubber latex and silica sol, the silica sol can in-situ generate SiO2 particles when heated. After coagulation of the mixed system, natural rubber/nanosilica composites C(NR/nSiO2) were obtained. The composites C(NR/nSiO2) and their vulcanizates were studied using a rubber processing analyzer (RPA), dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). The influence of silica contents on the C(NR/nSiO2) vulcanizates mechanical properties, cross-linking degree, Payne effect, dissipation factor (tanδ), and the particle size and dispersion of SiO2 in NR were investigated. The results obtained were compared with the NR/SiO2 composites based on traditional dry mixing of bale natural rubber and precipitated silica (white carbon black). The results showed that when using a sulfur curing system with a silica coupling agent ...

Supramolecular elastomer based on polydimethylsiloxanes (SESi) is a kind of novel elastomer cross-linked by the multihydrogen bonds supplied by the functional groups linked to the end of the PDMS chains, such as amide, imidazolidone, pending urea (1,1-dialkyl urea), and bridging urea (1,3-dialkyl urea). SESi showed lower glass transition temperature (T g) at about -113 °C because of the softer chain of PDMS, and could show real rubber-like elastic behaviors and acceptable water vapor transmission rate under room temperature. The high biocompatibility of SESi in the form of films was demonstrated by the cytotoxicity evaluation (MTT cytotoxicity assay and direct contact assay), hemolysis assay, and skin irritation evaluation. Based on detailed comparisons between commercial Tegaderm(™) film and SESi film using a full-thickness rat skin model experiment, it was found that SESi film showed similar wound contraction rate as that of Tegaderm(™) film on day seven, 10, and 14; only on day five, SESi film showed a significant (p 0.05) lower wound contraction rate. And, the wounds covered with SESi film were filled with new epithelium without any significant adverse reactions, similar with that of Tegaderm(™) film.

Novel self-healing supramolecular elastomers based on polydimethylsiloxanes (SESi) were synthesized from a mixture of polydimethylsiloxanes derivers with single, di-, or tri-carboxylic acid groups (PDMS–COOHx, where x = 1, 2, and 3, respectively), diethylene triamine, and urea with a two-stage procedure. The reactions and the final products were tracked, characterized, and confirmed by Fourier transform infrared spectroscopy, 1H-NMR, differential scanning calorimetry, dynamic mechanical analysis, and gel permeation chromatography. Compared with a supramolecular rubber based on dimer acid (reported previously) with a similar synthesis procedure, the SESi showed a lower glass-transition temperature of about −113°C for the softer chain of polydimethylsiloxane and showed real rubberlike elastic behavior and self-healing properties at room temperature or even lower temperatures. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Blends of poly(ethylene-co-vinyl alcohol) (EVOH) with maleic anhydride-grafted-poly(ethylene-octene) (POE-g-MAH) were prepared by blending extrusion in order to improve the toughness and flexibility of EVOH. The compatibility behavior of these blends with POE-g-MAH content range from 0 to 25 wt% was studied using mechanical, thermal, infrared, and morphology characterization techniques. The mechanical test results showed that POE-g-MAH can significantly improve the impact toughness of EVOH with a brittle-tough transition appeared at the POE-g-MAH content of 20 wt%. A huge increase of toughness of the blend was also observed when the POE-g-MAH content was increased to 15 wt%. The thermal analysis of the blends demonstrated that the thermal stability of EVOH is improved with the addition of POE-g-MAH, adding 20 wt% or more POE-g-MAH can effectively decrease the crystallinity of EVOH and greatly improve compatibility between the two components. The existence of esterification between anhydride groups in POE-g-MAH and hydroxyl groups in EVOH in melt processing was confirmed using Fourier transform infrared technique. Morphology analysis of the Izod impact fractures has clearly shown the mechanisms for these blends to change from brittle to tough with increasing the POE-g-MAH content. POLYM. ENG. SCI., 53:2093–2101, 2013. © 2013 Society of Plastics Engineers

Poly(ethene-co-1-butene)-graft-methyl methacrylate-acrylonitrile (PEB-g-MAN) was prepared by suspension grafting copolymerization of methyl methacrylate (MMA) and acrylonitrile(AN) onto PEB. PEB-g-MAN/SAN resin blends (ABMS) were prepared by blending PEB-g-MAN with styrene-acrylonitrile copolymer (SAN resin). The effects of AN/(MMA+AN) feed ratio (fAN), PEB/(PEB+MMA+AN) feed ratio (fPEB) and benzoyl peroxide (BPO) dosage on the monomer conversion ratio (CR), rubber's grafting ratio (GR), grafting efficiency (GE) of the copolymerization and the toughening effect of PEB-g-MAN on the SAN resin were investigated. FTIR quantitative analysis showed that when the weight percent of AN unit in the unextracted product was 21.5 wt% with fAN of 25 wt%, the toughening effect of unextracted PEB-g-MAN on SAN resin was the highest. Gel permeation chromatography (GPC) analysis showed that when fAN was 25 wt%, the grafted copolymer had the lowest molecular weight and ABMS had highest toughness. Transmission electron micros...

POE-graft-methyl methacrylate and acrylonitrile (POE-g-MAN) was prepared by suspension graft copolymerization of methyl methacrylate (MMA) and acrylonitrile (AN) onto polyethylene-octene copolymers (POE). POE-g-MAN/SAN resin blends (AOMS) were prepared by blending POE-g-MAN with styrene-acrylonitrile copolymer (SAN resin). The effects of reaction conditions on the graft copolymerization and the toughening effect of POE-g-MAN on SAN resin were discussed. The results showed that the optimized reaction conditions were AN/(MMA + AN) ratio of 15 wt%, POE/(POE + MM − AN) ratio of 60 wt%, BPO/(POE + MMA − AN) ratio of 1 wt%, toluene dosage of 44.4 wt%, PVA dosage of 0.4 wt%, SDS dosage of 0.07 wt%, aqueous phase/oil phase mass ratio of 1.5, at 80 °C for 20 h, and when the POE/AOMS mass ratio was 25 wt% under the optimized reaction conditions, the notched Izod impact strength of AOMS reached 54.0 kJ/m2. Fourier transform infrared spectroscopy provided substantial evidence of grafting of MMA and AN onto POE chains, and differential scanning calorimetry showed that the graft branches affected the crystallization of POE chains and made the melt temperature and the fusion heat be lower. Transmission electron microscopy analysis showed that the highest toughness occured when the size of POE-g-MAN particles and the surface to surface interparticle distance were proper. Scanning electron microscopy analysis indicated that the AOMS fracture surface had plastic flow visible which looked like a fibril morphology when POE content was 25 wt% with the AN/(MMA + AN) ratio (f AN) of POE-g-MAN of 15 wt%. The toughening mechanism of AOMS was shear yielding of matrix, which endowed AOMS with remarkable toughness. Dynamic mechanical thermal analysis showed that the compatibility of the POE phase and SAN phase improved after graft copolymerization of MMA and AN onto POE.

Carbon black (CB) filled powdered natural rubber [P(NR/N234)] was prepared using a patented method of latex/CB coagulation technology. The influence of curing recipes and CB contents on the curing, mechanical, and dynamic properties were studied in depth, and the results were compared with that of NR/N234 compounds based on traditional dry mixing of bale NR and CB. The results showed that, compared with NR/N234, P(NR/N234) showed higher tensile strength, tear strength, rebound elasticity and flexibilities, and the antiabrasion properties were similar, while the dynamic temperature-build-up and dynamic compression permanent set were about 50% of that of NR/N234. The analysis based on scanning electron micrographs (SEM) and the Payne effect showed that the fine dispersion of CB in the rubber and the enhanced interaction between CB and rubber contributed to the excellent properties of P(NR/N234), sufficient that they make P(NR/N234) a potential material for the tread compounds of heavy-duty all-steel cord ra...

POE-graft-methyl methacrylate and acrylonitrile (POE-g-MAN) was prepared by graft copolymerization of methyl methacrylate (MMA) and acrylonitrile (AN) onto polyethylene-octene copolymers (POE) with suspension polymerization. POE-g-MAN/SAN resin blends (AOMS) were prepared by blending POE-g-MAN with styrene-acrylonitrile copolymer (SAN resin). The mechanical properties, compatibility, and thermal stabilities of AOMS were studied. The notched impact strength of the blends reached 54.0 kJ/m2 when the AN/(MMA + AN) ratio (fAN) of POE-g-MAN, benzoyl peroxide dosage, and POE content in AOMS were 15 wt%, 1.0 wt%, and 25 wt%, respectively. Transmission electron microscopy analysis showed that the highest toughness occurred when the size of POE-g-MAN particles and the surface-to-surface inter-particle distance were proper. Scanning electron microscopy analysis indicated that the AOMS fracture surface had plastic flow visible, which looked like a fibril morphology when the AN/(MMA + AN) ratio (fAN) of POE-g-MAN was...

EPM-graft-methyl methacrylate and acrylonitrile (EPM-g-MAN) was synthesized by graft copolymerization of methyl methacrylate (MMA) and acrylonitrile (AN) onto ethylene—propylene bipolymer (EPM) using the method of suspension polymerization. A novel engineering plastic with high impact strength, AEMS, which shows excellent resistance to weatherability and yellow discoloration and aging properties, were prepared by blending EPM-g-MAN with styrene—acrylonitrile (SAN) resin. The influence of the suspension grafting copolymerization technologies, including monomer ratios, EPM ratios, initiator content on monomer conversion ratio, grafting ratio, grafting efficiency, and the impact strength of AEMS, were investigated. The result showed that the optimized reaction conditions were obtained when the mass ratio of AN/MMAAN(fAN) was 15 wt%, the mass ratio of EPM/(EPM + MMA-AN) was 60 wt%, and the mass ratio of BPO/(EPM + MMA-AN) was 0.6 wt%. When the EPM/ AEMS mass ratio was 25 wt%, the notched Izod impact strength of AEMS reached 55.9 kJ/m2. DSC and DMA analysis showed that the compatibility of EPM-g-MAN and SAN resin improved when the grafting chain polarity was appropriate. Transmission electron microscopy analysis showed that EPM phase was the near continuous phase in the shape of bead string with diameter of about 0.15 μm and had good compatibility with SAN resin. Scanning electron microscopy analysis indicated that AEMS fracture surface appeared ‘root beard’ morphology. These phenomena indicated that the toughening mechanism was shear yielding of matrix, which endowed AEMS with remarkable toughness.

Poly(ethene-co-1-butene)-graft-methyl methacrylate-acrylonitrile (PEB-g-MAN), synthesized by suspension grafting copolymerization of methyl methacrylate and acrylonitrile onto PEB, was blended with styrene-acrylonitrile copolymer (SAN). The mechanical properties, phase structure, toughening mechanism, miscibility, and thermal stability of the SAN/PEB-g-MAN blends were studied using a pendulum impact tester, tension tester, scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic mechanical analysis (DMA), and thermogravimetric analysis (TG). The results showed that PEB-g-MAN has an excellent toughening effect on SAN resin. The notched impact strength of the blends (containing 25 wt% PEB) was 63.3 kJ/m2, which was nearly 60 times that of SAN resin. The brittle-ductile transition of SAN/PEB-g-MAN blends occurred when the weight percentage of PEB was between 17.5 and ∼20 wt%. SAN and PEB-g-MAN were partially miscible. The toughening mechanism of the blends changed with the PEB cont...

Ethylene–propylene–diene–methyl methacrylate/acrylonitrile terpolymers (EPDM-g-MAN) were synthesized by comonomers methyl methacrylate and acrylonitrile (MMA-AN) grafted on EPDM macromolecules with solution graft copolymerization. The engineering plastics of the blend of EPDM-g-MAN with SAN (AEMS) were prepared by blending EPDM-g-MAN with SAN resin. The effect of AN/MMA-AN weight percentage (f AN) on monomer conversion ratio, grafting ratio, and grafting efficiency of the graft copolymerization and the notched Izod impact strength of AEMS were investigated. The notched Izod impact strength of AEMS, prepared by blending SAN with EPDM-g-MAN, was synthesized under our optimum S2 reaction conditions, with EPDM/MMA-AN weight proportion of 50/50 and f AN of 10 wt%, presenting a peak with the maximum value of 61.0 kJ/m2. The microstructure of AEMS prepared with S2 reaction conditions showed that when the polarity of EPDM-g-MAN was appropriate, the EPDM phase formed a pseudocontinuous phase in the SAN matrix and ...

Star-shaped hydroxy-terminated poly(d,l-lactide) (s-PDLLA), with arms of different lengths, were obtained by ring-opening polymerization (ROP) of d,l-lactide (LA) initiated by varied contents of pentaerythritol (PETH) in the presence of stannous octoate (Sn(Oct)2), and were condensed with carboxyl-terminated poly(ethylene glycol) methyl ether (CT-mPEG, M n = 850 and 2,000) to afford four-arm star-shaped poly(d,l-lactide)-block-poly(ethylene glycol) copolymer (s-PDLLA-b-PEG). The polymers, including s-PDLLA, CT-mPEG, and s-PDLLA-b-PEG, were characterized and confirmed by 1H-NMR and 13C-NMR spectroscopy, fourier transform infrared spectroscopy (FT-IR), and gel permeation chromatography (GPC).

EPDM-graft-methyl methacrylate and styrene (EPDM-g-MS) were synthesized by solution graft copolymerization of methyl methacrylate (MMA) and styrene (St) onto ethylene-propylene-diene terpolymer (EPDM). EPDM-g-MS/MS resin blends (MES) tht were prepared by melt blending EPDM-g-MS and methyl methacrylate-styrene copolymer (MS resin). The mechanical properties, compatibility, thermal stabilities and rheological properties of MES were studied by the pendulum impact tester and the tension tester, differential scanning calorimetric (DSC), thermogravimetry analysis (TGA), and the capillary rheometry, respectively. The results showed that EPDM-g-MS had an excellent toughening effect on MS resin; the notched Izod impact strength of MES reached 20.7 kJ/m2 when EPDM content in MES was 25 wt%, about 14 times that of MS resin. EPDM-g-MS and MS resin were partially compatible, and the compatibility increased with an increasing MMA/St ratio of EPDM-g-MS. MES had excellent heat-resistance, which increased as the EPDM cont...

Powdered carbon black filled natural rubber, P(NR/HAF), is a premixture of natural rubber and carbon black in powdered form with good carbon black dispersion throughout the rubber matrix. In this study, the mastication properties of P(NR/HAF) were observed under a wide temperature range (50–110°C) and rotor speed (30–100 rpm) range, using a mixing head attached to Brabender Plasticorder. It was found that P(NR/HAF) showed different mastication characteristic, compared to the traditional internal mastication theories of natural rubber; poor masticating properties of P(NR/HAF) are observed with low rotor speed and high temperature and a ‘‘stable zone’’ with middle rotor speed and lower temperature. The Mooney viscosity of rubber batch under different rotor speed and temperature was almost the same, and mastication properties were unsatisfactory. It was considered that the higher temperature build-up of the mixing batch of P(NR/HAF) during the early stage of internal mixing results in the special mastication properties. A quadratic mastication model of P(NR/HAF), based on the multivariate regression analysis and stepwise regression analysis, was used to predict the mastication characters of P(NR/HAF) in internal mixer under varied temperature and rotor speed. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers

EPDM-graft-methyl methacrylate and styrene (EPDM-g-MMA-St) was synthesized by solution graft copolymerization of methyl methacrylate (MMA) and styrene(St) onto ethylene-proplene-diene terpolymer (EPDM) in toluene/n-heptane cosolvent using benzoyl peroxide as an initiator. Fourier transform infrared spectroscopy provides a substantial evidence of grafting of MMA and St onto EPDM. EPDM-g-MMA-St/MS resin blends (MES) were prepared by melt blending EPDM-g-MMA-St and MS resin, and the toughening effects of EPDM-g-MMA-St on MS resin were studied. The results showed that the synthesized conditions of EPDM-g-MMA-St influenced the toughening effect of EPDM-g-MMA-St on MS resin. Notched Izod impact strength of MES increased with increasing grafting ratio, grafting chain polarity of EPDM-g-MMA-St, and EPDM content in MES. Differential scanning calorimetry showed that EPDM-g-MMA-St and MS resin are compatible partially and the compatibility improves with increasing grafting chain polarity of EPDM-g-MMA-St. Transmission electron microscopy and scanning electron microscopy analysis showed that the phase structure was “sea-island” structure, and the particle diameter of EPDM-g-MMA-St increased, meanwhile, surface to surface interparticle distance decreased with an increase in EPDM content, which resulted in the toughening mechanism of MES changed into slight shear yielding of matrix from the damage mode of cavitation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Ten types of rare earth (RE) compounds modified carbon black (HAF-RE) were prepared using chemical-deposit method, then HAF-RE were mixed with natural rubber latex to prepare HAF-RE filled powdered natural rubber [P(NR/HAF-RE)] by a carbon black/rubber latex coagulation method. It is found that most of the P(NR/HAF-RE) vulcanizates showed better mechanical properties, especially higher tensile modulus, and tensile strength, compared with none-rare earth modified carbon black filled powdered natural rubber [P(NR/HAF)]. Dysprosium (Dy) modified carbon black (HAF-Dy) filled powdered natural rubber [P(NR/HAF-Dy)] was chosen for intensive investigation because of its better comprehensive mechanical properties. It is found that the adding of Dy compounds could help to get smaller particles with narrower particle size distribution, and results from the SEM analysis show that carbon black has been dispersed in rubber matrix uniformly with diameter of 50–150 nm. The TEM analysis showed that Dy compounds could obviously reduce the aggregation of primary particles of carbon black, and promote the dispersion of carbon black in P(NR/HAF-Dy) particles. © 2008 Wiley Periodicals, Inc. JAppl Polym Sci 2008

Supramolecular elastomers (SESis) were synthesized via a simplified synthesis route on the basis of a linear bifunctional polydimethylsiloxane. Compared with previous synthesis methods, the structure of the product was much clearer. The 1H-NMR titration results show that the hydrogen-bond associations in SESis were relatively weak. During 1H-NMR reaction monitoring, the viscosity analysis of SESis and the model reactions demonstrated a previously neglected covalent crosslinking reaction not only during the reaction process but also during the postprocess; this led to a hybrid network, that is, covalent crosslinking and hydrogen association, in SESis. This finding explained the poor solubility of the SESis, and it provides us with an important way to controllably synthesize this material and adjust its properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43385.

EPDM-graft-methyl methacrylate and styrene (EPDM-g-MS), a toughen agent for MS resin, was synthesized by solution graft copolymerization of methyl methacrylate (MMA) and styrene (St) onto ethylene-proplene-diene terpolymer (EPDM) in toluene/n-heptane cosolvent using benzoyl peroxide (BPO) as an initiator. The effects of reaction conditions on the graft copolymerization were discussed. EPDM-g-MS/MS resin blends, a novel high impact engineering plastic, was prepared by melt blending EPDM-g-MS and MS resin. The toughening effect of EPDM-g-MS on MS resin was investigated. The results showed that the optimized reaction conditions were EPDM/MMA-St ratio of 50/50, MMA/St ratio of 75/25, initiator dosage of 1%, reactant concentration of 20%, toluene/n-heptane ratio of 75/25, at 80 °C for 20h, and EPDM-g-MS with the higher EPDM content (56.8%) and grafting ratio (52.8%) was obtained under the optimized reaction conditions. SEM analysis showed that EPDM-g-MS had good compatibility with MS resin. EPDM-g-MS had excellent toughening effect on MS resin and could be used for toughen agent of MS resin.

Styrene-EPDM-acrylonitrile tripolymer (EPDM-g-SAN) was synthesized by the graft copolymerization of styrene (St) and acrylonitrile (An) onto ethylene-propylene-diene terpolymer (EPDM) with “phase inversion” emulsification technique. The high impact strength engineering plastics AES was the blend of SAN resin and EPDM-g-SAN, which occupied good weathering and yellow discoloration resistivity. The effects of An percentage in comonomer and the weight proportion of EPDM to St-An on graft copolymerization behavior and AES notched impact strength were studied. The results showed that monomer conversion ratio (CR) exhibited a peak when the An percentage changed, and the maximum value was 97.5%. Grafting ratio (GR) and grafting efficiency (GE) enhance as well. The notched impact strength of AES presented a peak with the maximum value of 53.0 KJ/m2, when An percentage was at the range of 35–40%. The spectra of FTIR showed that St and An were graft onto the EPDM. DSC analysis illuminated that Tg of EPDM phase in the blends was lower than that of the pure EPDM. TEM and SEM micrographs indicated that the polarity of g-SAN of EPDM-g-SAN was the main factor effect the particle morphology, in terms of size, distribution and isotropy. When weight ratio of St to An was 65/35, the polarity of g-SAN chains was appropriate, and the EPDM-g-SAN particles dispersed well in the SAN matrix. The super impact toughness is interpreted in terms of EPDM phase cavitation and enhanced plastic shear yielding. The highest toughness occurs at an optimum EPDM-g-SAN phase particle size which is about 0.2 μm in SAN resin matrix. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Carbon black (HAF) filled powdered natural rubber (P(NR/HAF)) was prepared and the particle size distribution, mechanical properties, and micromorphology of P(NR/HAF) were studied. A carbon black–rubber latex coagulation method was developed for preparing carbon black filled free-flowing, noncontact staining NR powders with particle diameter less than 0.9 mm. A powdering mechanism model was put forward to describe the powdering process, which shows that the key technical points consist in the surfactant with good emulsification properties and the polymer coating resin with good film forming properties. SEM analysis shows that carbon black and rubber matrix have formed a macroscopic homogenization in the P(NR/HAF) particles without contact staining, and carbon black particles are well dispersed in rubber matrix with diameter of about 50–150 nm. P(NR/HAF) vulcanizate showed better mechanical properties than bale natural rubber/carbon black blends (NR/HAF) and simple NR latex/carbon black blends (NRL/HAF), which depends primarily upon the absence of free carbon black, the fine dispersion of filler on the rubber matrix, and the better interaction between carbon black and rubber matrix due to the proper preparation condition of noncontact staining carbon black filled powdered NR. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1763–1774, 2006

The premature vulcanization behaviors of six kinds of common rubber (NR, BR, SBR, NBR, CR, and EPDM) compounds containing curing agents were studied in a wide processing temperature range (100–140°C) and rotor speed range (30–70 rpm) using a Brabender torque rheometer, which can supply the rubber compounds a high shear rates processing condition. After comparison with the Mooney scorch time (MSt5), it is shown that Mooney scorch time cannot predict the premature vulcanization time under high shear rate processing. Six models were put forward based on the data obtained from the Brabender mixing head. The regression analysis and variance analysis showed that these models could simulate the premature vulcanization time very well. An explanation was given based on the reactivity and of rubber chain segments: the increasing reactivity and the impact probability of reactive rubber chain segment under high shear rate is the main reason of shorter scorch time of rubber compounds under high shear rate internal mixing. © 2006 Wiley Periodicals, Inc. JAppl PolymSci 102: 5414–5420, 2006

High-abrasion furnace black (HAF, grade N330) filled nonsulfur modified powdered polychloroprene rubber [P(CR231/HAF)] was prepared with the method of carbon black–rubber latex coagulation using CR231 latex as raw rubber material, HAF as reinforcing filler, and polymeric resin as coating resin. The influence of the content of dispersing agent and coating resin on contact staining and dispersion properties of carbon black in P(CR231/HAF) were investigated. The results show that the addition of dispersing agent and coating resins can decrease the contact staining level of carbon black effectively. When the dispersing agent/HAF (w/w) ratio was 0.12 or 0.1, 10 phr coating resin was added, and P(CR231/HAF) without contact staining can be prepared. The analysis on scanning electron microscopy and surface energy spectrum showed that free carbon black crumb on the surface and inner of P(CR231/HAF) particles causes its contact staining. The well dispersion of carbon black in the P(CR231/HAF) can eliminate contact staining effectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 192–196, 2006

Sulfur-modified powdered polychloroprene rubber (PCR-121) was prepared by inverse coagulation. A new coating agent (SN) was developed that could generate in situ the coating layer by inverse coagulation. The results show that this is a low-cost, stable technology for the production of powdered rubber with a very low coating agent content. A powdering model based on the liquid–liquid stirring theory of noncoalescing, liquid–liquid dispersion was proven with uniform design testing. According to this model, the mass fraction of medium-scale particles (1–3 mm) was only related to the agitation speed in the experimental range. Scanning electron microscopy (SEM) analysis showed that the PCR-121 particles were single continuous particles coagulated from single chloroprene rubber latex drops. Energy spectrum analysis showed that a layer with higher Ca content was coated at the surface of PCR-121 particles, which made PCR-121 a free-flowing powdered rubber. The results show that the variation of Mooney viscosity (ML1+4 100°C) from 30 to 130 had no obvious effect on the mechanical properties of PCR-121. Compared with bale CR121, PCR-121 had better mechanical properties. SEM analysis and energy spectrum analysis on the tensile fracture surfaces showed that the dispersion of compounding agents in PCR-121 was better than that in bale CR121, which resulted in better mechanical properties in PCR-121. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2109–2115, 2005

The surface modification of nano calcium carbonate (nCaCO3) particles was carried out with a soluble compound of lanthanum via a coating process of chemical deposition, and nCaCO3 particles covered with a compound of lanthanum (nCaCO3La) were prepared. The polypropylene (PP)/nCaCO3 and PP/nCaCO3La composites were prepared with a two-roll mill. The measurements of the mechanical properties showed that the impact strength of the composites increased at first and then decreased with the addition of fillers, and the tensile strength was reduced at the same time. The impact strength of PP/nCaCO3La was higher than that of PP/nCaCO3, and the impact strength of PP/nCaCO35La was three times that of virgin PP. Transmission electron microscopy and scanning electron microscopy showed that nCaCO3La dispersed well in the PP matrix, the size distribution of the particles was uniform, and nCaCO3La adhered to the PP matrix very closely. The crystallization properties of virgin PP and its composites were studied with differential scanning calorimetry and wide-angle X-ray diffraction. The results showed that the β-PP phase easily formed with the addition of the lanthanum compound. In comparison with virgin PP, the addition of nCaCO3La led to a higher crystallization temperature. The size of the crystallites increased with the addition of nCaCO3La, and the nucleation of PP crystalline was also improved. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1154–1160, 2005

High-abrasion furnace black (HAF, grade N330)–filled powdered styrene butadiene rubber [P(SBR/HAF)] was prepared and the particle size distribution, mixing behavior in a laboratory mixer, and mechanical properties of P(SBR/HAF) were studied. A carbon black–rubber latex coagulation method was developed for preparing carbon black–filled free-flowing, noncontact staining SBR powders, with particle diameter less than 0.9 mm, under the following conditions: carbon black content > 40 phr, emulsifier/carbon black ratio > 0.02, and coating resin content > 2.5 phr. Over the experimental range, the mixing torque τα of P(SBR/HAF) was not as sensitive to carbon black content and mixing temperature as that of HAF-filled bale SBR (SBR/HAF), whereas the temperature build-up ΔT showed little dependency on carbon black content. Compared with SBR/HAF, P(SBR/HAF) showed a 20–30% mixing energy reduction with high carbon black content (>30 phr), which confers to powdered SBR good prospects for internal mixing. Carbon black and the rubber matrix formed a macroscopic homogenization in P(SBR/HAF), and the incorporation step is not obvious in the internal mixing processing results in these special mixing behaviors of P(SBR/HAF). A novel mixing model of carbon black–filled powdered rubber, during the mixing process in an internal mixer, was proposed based on the special mixing behaviors. P(SBR/HAF) vulcanizate showed better mechanical properties than those of SBR/HAF, dependent primarily on the absence of free carbon black and a fine dispersion of filler on the rubber matrix attributed to the proper preparation conditions of noncontact staining carbon black–filled powdered SBR. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2494–2508, 2004

Formed by noncovalent bonds, supramolecular polymer materials could form a dynamic network and then exhibit the ability to heal their damages. Actually, as an emerging and fascinating field, supramolecular self-healing materials have been developed for a decade. Because of the characteristics of noncovalent interaction, such as reversibility and self-repairing, these materials are being employed for a range of applications. In this chapter, some recent advances of supramolecular self-healing materials based on noncovalent interactions, including hydrogen bonding, π–π stacking, metal–ligand complexes, and ionomers are enumerated. Furthermore, the self-healing properties and mechanisms of these materials are described. Finally, their defects and prospects are also discussed.

A novel supramolecular elastomer (SESi) based on multiple hydrogen bond associations between low-molecular-weight polydimethylsiloxane chains was obtained through a two-step reaction of linear carboxyl-terminated polydimethylsiloxane oligomers with diethylenetriamine and urea, and the reaction mechanism was characterized. The results of differential scanning calorimetry and X-ray diffraction analyses indicated that the supramolecular network structure is completely amorphous, endowing SESi with rubber-like elastic behavior at room temperature. The transparent SESi film prepared by hot pressing displayed nice viscoelasticity, benign water absorption, water vapor transition rates, and ideal biocompatibility; and did not show cytotoxicity or skin irritation. These properties allow the elastomer to function as an occlusive wound dressing. To demonstrate its potential in wound dressings, a detailed comparison of commercial 3M Tegaderm™ film and the SESi film was conducted. The SESi film exhibited similar effects in wound healing, and the wound bed was covered by the SESi film without the occurrence of significant adverse reactions.

Compared with linear diblock or triblock poly(ethylene glycol)-block-poly(L-lactic acid) copolymer (PEG-b-PLLA), star-shaped PEG-b-PLLA (sPEG-b-PLLA) copolymers exhibit smaller hydrodynamic radius and lower viscosity and are expected to display peculiar morphologies, thermal properties, and degradation profiles. Compared with the synthesis routine of PEG-b-PLLA form lactide and PEG, the traditional synthesis routine from LA and PEG were suffered by the low reaction efficiency, low purity, lower molecular weight, and wide molecular weight distribution. In this article, multiarm sPEG-b-PLLA copolymer was prepared from multiarm sPEG and L-lactic acid (LLA using an improved method of melt polycondensation, in which two types of sPEG, that is, sPEG1 (four arm, Mn = 4300) and sPEG2 (three arm, Mn = 3200) were chosen as the core. It was found the molecular weight of sPEG-b-PLLA could be strongly affected by the purity of LLA and sPEGs, and the purification technology of vacuum dewater and vacuum distillation could help to remove most of the impurities in commercial available LLA. The polymers, including sPEG and sPEG-b-PLLA with varied core (sPEG1 and sPEG2) and LLA/sPEG feeding ratios, were characterized and confirmed by 1H-NMR and 13C-NMR spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and gel permeation chromatography, which showed that the terminal hydroxyl group in each arm of sPEGs had reacted with LLA to form sPEG-b-PLLA copolymers with fairly narrow molecular weight distribution. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Preparations of coxsackievirus B1 (CVB1) derived from an infectious cDNA clone have been crystallized in multiple crystal forms. Using high intensity synchrotron radiation, an orthorhombic form of the crystals was shown to diffract X-rays to at least 2.9 A resolution. The unit cell has a primitive lattice with dimensions a = 323 A, b = 450 A, and c = 522 A. A crystallographic asymmetric unit of these CVB1 crystals probably contains an entire virus particle, implying the presence of 60-fold non-crystallographic redundancy. This CVB1 crystal form appears to be suitable for high-resolution structure determination by X-ray crystallography.