Runguo Wang

Design and preparation of bio-based dielectric elastomer with polar and plasticized side chains

A new dielectric elastomer with large actuated strain driven by low electric field was synthesized from di-n-butyl itaconate and isoprene through free radical redox emulsion polymerization. The effect of the copolymerized proportion of poly(di-n-butyl itaconate-co-isoprene) (PDBII) and the dosage of crosslinking agent on the elastic modulus, dielectric properties, and actuated strain of the elastomer were investigated, and a potential dielectric elastomer candidate containing 70 wt% di-n-butyl itaconate was obtained. The permittivity of the PDBII crosslinked by 3.0 phr of dicumyl peroxide was 5.68 at 103 Hz, which was higher than that of commercial acrylic and silicone dielectric elastomers. Without any prestrain, an actuated strain of 20% was obtained at an electric field of 30 kV mm−1. In order to further increase the actuated strain, barium titanate (BaTiO3), a high-dielectric-constant ceramic powder, was utilized to fill the PDBII to form a BaTiO3/PDBII composite. The dielectric constant of the composite increased with increasing content of BaTiO3, and the elastic modulus of the composite was lower than that of the unfilled PDBII, leading to a larger dielectric actuated strain of the composite.

Preparation of graphene oxide/bio-based elastomer nanocomposites through polymer design and interface tailoring

Bio-based poly(dibutyl itaconate-ter-isoprene-ter-4-vinylpyridine) (PDBIIVP) elastomers with different 4-vinylpyridine (4-VP) contents were synthesized by redox emulsion polymerization for the purpose of designing and preparing green graphene oxide (GO)/PDBIIVP nanocomposites with strong interfacial interaction. The ionic bonding interfaces in the nanocomposites were the result of electrostatic attraction between the in situ protonated pyridine groups of PDBIIVP and the electronegative GO sheets with hydrochloric acid during latex co-coagulation and were confirmed by X-ray photoelectron spectroscopy. The inclusion of a small amount of 4-VP (less than 7 wt%) improved the dispersion of GO, the interfacial interaction between PDBIIVP and GO, and the performance of the GO/PDBIIVP nanocomposite markedly. The reinforcement effects of GO on the mechanical and gas barrier properties of PDBIIVP increased continuously with increasing 4-VP content. Additionally, GO/PDBIIVP nanocomposites with a fixed 4-VP content and different GO loadings were prepared and characterized. As the GO loading increased, the performance of the nanocomposites improved greatly. For the GO/PDBIIVP with 7.0 wt% of 4-VP and 4 phr of GO, the tensile strength increased by 700%, the volume loss of abrasion decreased by 53%, and the gas permeability decreased by 63% compared with those of the neat PDBIIVP. The remarkable improvements are attributed to the strong ionic bonding interfaces between the pyridine-included bio-based elastomer and GO. We believe that this work of new polymer construction with the functional group targeting the interfacial interaction with GO should be an important strategy for developing GO-based polymer nanocomposites with high performance.

Direct copolycondensation of biobased elastomers based on lactic acid with tunable and versatile properties

Novel poly(lactate/butanediol/sebacate/itaconate) (PLBSI) copolyesters with sustainability and biocompatibility were synthesized by using direct melting polycondensation. The molecular weights, chemical structures, and compositions of the copolyesters were confirmed by GPC, NMR, and FTIR. By controlling the content of lactic acid, the copolyesters were transformed from rigid plastics to flexible elastomers. The PLBSI elastomers were highly reinforced with nanosilica which can meet the tensile strength requirements for the majority of rubber products. More importantly, the PLBSI elastomers can be used as PLA tougheners owing to the similar lactate structures of PLA and PLBSI. The toughened PLA can be applied as excellent three-dimensional printing ink. Besides, the crosslinked PLBSI plastics were demonstrated to be promising shape memory polymers with excellent shape fixity and recovery rate. The renewable monomers, relatively simple polymerization, and versatile performance make our PLBSI copolyesters promising for various medical and engineering applications.

High performance bio-based elastomers: energy efficient and sustainable materials for tires

Globally, we are faced with a massive growth in the number of urban vehicles. This growth comes at the cost of enormous fuel consumption, CO2 emissions and air pollution, commonly seen as a haze. With a strategy to fabricate low roll-resistance green tire elastomers from large-scale, bio-based chemicals, specifically itaconic acid, mono-alcohols and conjugated dienes, each of these problems can be reduced. By combining a molecular structural design with non-petroleum based silica and an in situ process to tune the viscoelastic properties of the elastomer composites, we have successfully manufactured silica/poly(di-n-butyl itaconate-co-butadiene) nanocomposite-based green tires that have very low roll-resistance, excellent wet skid resistance and good wear resistance, promote fuel efficiency and reduce our dependence on petrochemical resources. The results shown here open an important avenue for the synthetic rubber and automobile industry to ameliorate a major problem facing many cities worldwide, and also provide an effective route for resource sustainability.

Experimental study and molecular dynamics simulation of dynamic properties and interfacial bonding characteristics of graphene/solution-polymerized styrene-butadiene rubber composites

Graphene/solution-polymerized styrene-butadiene rubber (SSBR) composites were prepared by using three types of SSBR matrix with different vinyl contents. The dynamic properties, interfacial bonding characteristics, and fractional free volume (FFV) of the composites were studied through a combined experimental and molecular dynamics (MD) simulation approach. We found that as the vinyl content increases in the SSBR matrix, the grapheme/SSBR interfacial interaction increases, the FFV decreases, and the graphene dispersion is improved. The interfacial interaction, which is derived from the introduction of graphene, can increase the activation energy and limit the mobility of the SSBR chains. Additionally, MD simulations of the pullout of the graphene from SSBR matrix were carried out to explore the interfacial bonding characteristics at the molecular level, which show that the interaction energy, pullout energy, and shear stress between graphene and SSBR increase with the increase of the vinyl content. The modeling results were in good agreement with the experimental results. This present study is expected to deepen the understanding of the basic physics for graphene reinforced rubber nanocomposites, especially the interfacial bonding characteristics at the molecular level.

Synthesis and evaluation of bio-based elastomer based on diethyl itaconate for oil-resistance applications

Bio-based elastomer poly(diethyl itaconate-co-isoprene) (PDEII) was designed and synthesized by redox-initiated emulsion polymerization from diethyl itaconate and isoprene with mass ratio of 20:80, 40:60, 60:40 and 80:20. The number-average molecular weights of PDEII exceeded 140000 with relatively high yields. The physical properties of PDEII, such as glass transition temperatures and thermostability, were comparable with conventional synthetic elastomers and can be readily tuned by varying the ratio of diethyl itaconate to isoprene. The interaction between silica and PDEII macromolecules was effectively enhanced with the increase of diethyl itaconate content by endowing high polarity. The oil-resistance relevant properties of silica/ PDEII80 (80% diethyl itaconate, 20% isoprene) such as retention of tensile strength, retention of elongation at break and change in volume even surpass those of silica/NBR 240S after soaked in ASTM 3# oil at different temperatures.

Preparation and intermolecular interaction of bio-based elastomer/hindered phenol hybrid with tunable damping properties

Abstract In this research, crosslinked hybrids of a newly invented bio-based elastomer poly(di-isoamyl itaconate-co-isoprene) (PDII) and 3,9-bis[1,1-dimethyl-2{β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy}ethyl]-2,4,8,10-tetraoxaspiro[5,5]-undecane (AO-80) were designed and prepared by the mechanical kneading of the PDII/AO-80 hybrids at a temperature higher than the melting point of AO-80, followed by the crosslinking of PDII during the subsequent hot-pressing/vulcanization process. The microstructure, morphology, and mechanical properties of the hybrids were systematically investigated in each preparation stage by using DSC, FTIR, XRD, SEM, DMTA, and tensile testing. Part of the AO-80 molecules formed an AO-80-rich phase, but most of them dissolved in the PDII to form a very fine dispersion in amorphous form. The results of FTIR and DSC indicated that strong intermolecular interactions were formed between the PDII and the AO-80 molecules. Each PDII/AO-80 crosslinked hybrid showed a single transition with a higher glass transition temperature and significantly higher loss value (tan δ) than the neat PDII because of intermolecular interactions between the PDII and the AO-80 molecules. For instance, tan δ of PDII/AO-80 consisting of 100 phr AO-80 achieved 2.6 times as neat PDII. The PDII/AO-80 crosslinked hybrids with applicability at room temperature are potential bio-based damping materials for the future.

Synthesis and structure design of new bio-based elastomers via Thiol-ene-Click Reactions.

The additions of 2-mercaptoethanol to (S)-(-)-limonene via click reaction is described as an adaptable and efficient way to obtain alcohol functionalized renewable monomer for the synthesis of new cross-linkable bio-based elastomers. Thiol first reacted with the limonene endocyclic double bond and then reacted with the exocyclics double bond to form the difunctional monomer. The structure of the monomer was determined by using FTIR, (1)H NMR and mass spectrometry. Thermal Gravimetric Analysis (TGA) and Differential Scanning Calorimetrys (DSC) characterization exposed that this monomer could be used to synthesize elastomers with excellent and adaptable thermal properties. The molecular weight of the synthesized elastomer could reach 186kDaa via melting polycondensation route and the structure-properties relationship was deliberated. Finally, these elastomers were mixed with dicumyl peroxide (DCP) to form cross-linked elastomers with certain mechanical property, and the gel contents of the elastomers were confirmed by using Soxhlet extraction method.