Morphology and thermomechanical properties of natural rubber vulcanizates containing octavinyl polyhedral oligomeric silsesquioxane

Octavinyl polyhedral oligomeric silsesquioxane (OV-POSS) was synthesized and characterized by means of proton nuclear magnetic resonance (1H NMR) together with Fourier transform infrared spectroscopy (FT-IR). The nanocages were then introduced to natural rubber (NR) to afford organic-inorganic hybrid composites. Upon curing with dicumyl peroxide, the size of the dispersed phase was observed to decrease monotonically with increasing OV-POSS content, as depicted in scanning electron microscopy (SEM) images. This behavior differs significantly from that of analogous OV-POSS/NR vulcanizates cured with sulfur reported previously. To address this, the proportion of crosslinked OV-POSS was calculated using the results of FT-IR. The reaction enthalpy of the composites with different OV-POSS loading was recorded and analyzed by differential scanning calorimetry (DSC). A co-crosslinking reaction was suggested to play a crucial role in determining the morphologies of the composites. In addition, the agglomeration and crystallization of OV-POSS can also affect the morphologies of the composites.

In this study, it was aimed to investigate octavinyl‐polyhedral oligomeric silsesquioxane (OV‐POSS) incorporation into natural rubber (NR)/butadiene rubber (BR) elastomer blends as a potential compatibilizer. The effects of OV‐POSS loading levels on the thermal, mechanical, morphological, and dynamic‐mechanical properties of elastomer blends were explored. Fourier‐Transform Infrared Spectrometer (FTIR), Temperature Scanning Stress Relaxation (TSSR), and Differential Scanning Calorimetry (DSC) results revealed the conceivable effect of OV‐POSS nanoparticles in the vulcanization through reacting with sulfur and/or elastomers. Scanning Electron Microscope (SEM), X‐Ray Diffraction (XRD), and tensile test measurements supported the improvement of mechanical properties due to homogeneous dispersion at low loading levels. On the other hand, high amount of OV‐POSS incorporation (7 and 10 phr) resulted in a decrease in mechanical properties, owing to the agglomeration of nanoparticles. According to contact angle and Dynamic mechanical analysis (DMA) results, it could be concluded that OV‐POSS nanoparticles were localized at the interface of the elastomers and enabled the compatibilization of immiscible NR/BR blends.

The aim of this study was to produce crosslinked low-density polyethylene (LDPE) composites using peroxide and octavinyl polyhedral oligomeric silsesquioxane (OvPOSS) and to examine the shape memory behavior. The strategy was to use OvPOSS as a coagent to increase the crosslinking density and crosslinking efficiency while improving the mechanical and shape memory properties as well. The peroxide concentration, from 0.5 phr to 3.0 phr, was taken as the experimental parameter, with 4 phr OvPOSS added to all composites. The melt mixing route was applied similar to that which would be used industrially. The thermo-responsive shape memory properties near the melting point were examined in tension mode. The dispersion of OvPOSS in the LDPE matrix was observed via scanning electron microscopy and Si-mapping. In addition, the thermal, mechanical, structural, and rheological features of the novel LDPE/OvPOSS and LDPE/peroxide/OvPOSS systems were investigated. It was observed that the crosslinking density of LDPE increased in the presence of OvPOSS, which affected the mechanical, rheological and thermal properties and increased the shape recovery ratio of the LDPE.

Surface properties of octavinyl polyhedral oligomeric silsesquioxane (OVS), grafted polyurethane (PU) and heparinized carbon nanotubes (HCNTs) nanocomposite thin-films were evaluated, and the effect of OVS presence on platelet adhesion on the surface of nanocomposite films for artificial heart valve application was investigated using in-vitro tests. OVS was synthesized, then PU and CNT (PU/CNT) nanocomposite films were dipped in the solution of OVS in toluene for grafting. Synthesized OVS was investigated by XRD, FTIR, and NMR tests. SEM-EDX micrographs showed that the morphology of the PU/HCNT surface was obviously changed due to OVS grafting. Surface studies proved OVS grafting on the surface. Surface roughness was increased after grafting PU/HCNT surface with OVS in comparison to the untreated PU/HCNT nanocomposite surface. The contact angle was increased from 88° for PU/HCNT sample to 165° for OVS-grafted PU/HCNT sample. After the addition of CNTs to the matrix, the modulus was increased. According to the MTT test, modified polymeric nanocomposite has no cytotoxicity, and the adhesion of L929 fibroblast cells on the grafted surface was increased. Its shown in the platelet adhesion test that blood compatibility of the OVS grafted films are increased in comparison with PU/HCNT. Surface calcification of OVS-grafted PU/HCNT was reduced according to the in-vitro calcification test. It has been concluded that the combination of physical and mechanical properties of PU/HCNT and the calcification resistance of OVS is a suitable achievement for heart valve application.

Using organic coatings helps to protect PET (polyethylene terephthalates) surfaces, improve surface hardness, scratch resistance, and solvent resistance, prolong the service life of PET film, and to expand their scope of applications. There were some disadvantages, including poor flexibility and impact resistance in high-hardness coatings; organic coatings should also be modified to improve the toughness. Herein, a UV (ultraviolet curing) curable high-hardness organic coating used in PET surface protection was prepared and modified with inorganic nanoparticles, such as OVPOSS (octavinyl-polyhedral oligomeric silsesquioxane). The effects of the categories of nanoparticles on the coating performance were studied. UV-Vis spectra (ultraviolet visible light spectra), FT-IR (Fourier transform infrared spectrometer), TGA (thermogravimetric analysis), DMA (dynamic-mechanical), SEM (field emission scanning electron microscope), and AFM (atomic force microscope) were used to characterize the properties of the coatings. The results showed that the addition of eight-vinyl POSS to the organic coating significantly increased its glass transition temperature (Tg) from 100 to 120 °C, improved its storage modulus from 167.6 to 258.9 MPa, and raised its impact resistance and flexibility. The SEM and AFM images displayed that the eight-vinyl POSS particles were dispersed homogeneously in the coating, arranged in an ordered network, and had good compatibility with organic components. The film displayed excellent properties, including 4 H of the pencil hardness, 100 g cm of impact resistance, excellent flexibility, and 90% of light transmittance, with the addition of 0.3 wt % OVPOSS. TGA analysis revealed that the coating had good thermal stability, with 5% weight loss temperature up to 335 °C.

The preparation of a novel fast response thremosensitive hydrogel was investigated by incorporating nanosized octavinyl polyhedral oligomeric silsesquioxane (OvPOSS) particles into inorganic clay-crosslinked poly(N-isopropylacrylamide) (PNIPA) nanocomposites hydrogels (NC gels). The resulting hydrogels named as P-NC gels involving both the strategies of NC gels and double network gels (DN gels) were successfully synthesized via a two-step technique. The second PNIPA network crosslinked by OvPOSS were polymerized in the presence of the first clay-PNIPA network. The P-NC gels were characterized by FTIR, X-ray, DSC, UV/vis,spectra, SEM, mechanical properties and swelling behaviors measurements. The key factor for preparing homogenous P-NC gels with good transparency was the low concentration of OvPOSS (c(OvPOSS)) dispersed uniformly in polymer as a cross-linker. On the contrary, the high c(OvPOSS) led to the significant aggregation of the OvPOSS particles and thus resulted in the heterogeneity of gels. The SEM images of freeze-dried P-NC gels exhibited a highly interconnected microporous network structure, which could be adjusted by varying the amount of OvPOSS. The special porous morphology brought about an attractive faster swelling/deswelling rate than that of normal NC gels. All properties of P-NC gels displayed an obvious dependence on the concentration of incorporated OvPOSS. The excellent mechanical properties, tunable LCST, especially the fast deswelling rate make these hydrogels potential candidates for applications in drug release and other biological fields.

A series of poly(methyl methacrylate) (PMMA) containing octavinyl-polyhedral oligomeric silsesquioxane (OV-POSS) nanocomposites were synthesized by solution polymerization. The products were characterized by FTIR, 1H NMR, GPC, TEM, DSC and TGA. The actual contents of OV-POSS in the obtained products and the reaction degree of the vinyl groups in the POSS were calculated on the basis of FTIR, TGA and 1H NMR data respectively. The DSC and TGA results indicate that the incorporation of POSS molecules could improve the thermal properties of PMMA nanocomposites significantly. The glass transition temperature (Tg) and thermal decomposition temperature (Tdec1) of the nanocomposite with 12.27 wt % of OV-POSS were increased by 23 °C and 93 °C correspondingly. In our experiment, the improved thermal properties were largely attributed to the nanoreinforcement effect of POSS cages and the formation of star-shaped structures with cubic silsesquioxane core.

Novel and eco-friendly hydrophobic treatment of cotton and polyester fabrics based-on octavinyl and aminopropylisobutyl polyhedral oligomeric silsesquioxanes (OL-POSS and AM-POSS)

In this study, eggshell (ES) wastes were used as a renewable reinforcing material in natural rubber (NR) composite to limit carbon production. Long bio-alkyd resin (LAR) was also used to envelope the inorganic ES particles and to aid in dispersing the filler in the NR matrix. The effect of the coated ES filler (ESR) in the rubber mix on the morphology, mechanical properties, and swelling was investigated. The ES filler and its biocomposites were characterized by X-ray fluorescence, scanning electron microscopy, Fourier transform infrared imaging microscope (FT-IR-IM), differential scanning calorimetry (DSC), and thermogravimetric analysis. The morphological data reveal that the resin enhances the dispersion of the ES filler in the NR matrix. These data were confirmed by the results obtained from FT-IR-IM. The swelling and mechanical properties were significantly improved when the coated filler was used in NR matrix, especially at 20 wt.% ESR. DSC thermograms revealed that the increase in the resin caused the glass transition temperature (Tg) to be shifted to a lower temperature. The obtained results show that the bioenveloping ESR can be used as potential alternative for green tire and vehicle applications rather than conventional petroleum-based filler.

Submicron/nano-structured icephobic surfaces made from fluorinated polymethylsiloxane and octavinyl-POSS

Optically active hybrid particles consisting of chiral organic component and inorganic component integrate the individual advantages of the components in one entity. This article reports a new type of optically active hybrid particles constructed by helical substituted polyacetylene and octavinyl polyhedral oligomeric silsesquioxane (OvPOSS). The hybrid particles were prepared in a two‐step process. First, helical substituted polyacetylene with pendent vinyl groups was synthesized and named as macromonomer (MM). Then, hybrid particles were prepared from MM and OvPOSS by free radical suspension polymerization, in which OvPOSS acted simultaneously as comonomer and crosslinking agent. OvPOSS and MM together constituted a crosslinked network and formed spherical, porous hybrid particles. The resulting hybrid particles exhibited the desired optical activity, according to circular dichroism spectroscopy measurement. As an organic/inorganic hybrid molecule itself, OvPOSS moderately improved the thermostability of the organic component and meanwhile increased the porosity of the hybrid particles. It also helped to tune the surface morphology of the hybrid particles. The present study provides a novel class of optically active hybrid particles, and the preparation strategy may further work as a versatile platform for developing novel chiral hybrid materials.

Shape memory polymers are smart materials having the ability to change their shape under external stimulus. One of the most widely used shape memory polymers is cross-linked polyethylene (PE). The cross-linked polyethylene can be triggered by temperature to transfer from its permanent shape to programmed shape. Polyhedral oligomeric silsesquioxanes (POSSs) are the new generation of hybrid nanoparticles that positively affect the thermal stability, thermo-mechanical strength, flow properties and crystallization rates of the polymers. POSSs can also be used as crosslinking agents. Besides, coagents are used in order to improve the crosslinking efficiency by reducing undesirable side reactions such as chain breakage or disproportionation. They form bridges between polymer chains to be cross-linked. The aim of this study is to investigate the synergistic effects between POSS and coagent on the physical and shape memory properties of cross-linked linear low-density polyethylene (LLDPE). Octavinyl POSS (OvPOSS) nanoparticles and poly(ethylene glycol) dimethacrylate (PEGDMA) were used as coagents in this study. The peroxide used in crosslinking was di tert-butyl cumyl peroxide (PRX). Its content was kept constant as 1 phr. LLDPE/OvPOSS/PRX, LLDPE/PEGDMA/PRX and LLDPE/OvPOSS/PEGDMA/PRX composites were prepared in an Xplore model micro-compounder at a screw speed of 50 rpm and 135°C barrel temperature. The crosslinking was carried out using a hot-press operated at 175°C. The samples were characterized by performing differential scanning calorimetry (DSC), scanning electron microscopy (SEM), rheology, tensile tests and shape memory tests. Rheological analysis showed that the degree of crosslinking, storage modulus and complex viscosity increased in the presence of OvPOSS and PEGDMA. A synergistic effect was observed between OvPOSS and PEGDMA coagents.

Hydrogels based on pH-sensitive polymers are of great interest as potential biomaterials for the controlled delivery of drug molecules. In this study, a novel pH-sensitive copolymer hydrogel based on acrylic acid (AA) monomer by free-radical solution polymerization were synthesized with organic–inorganic cross-linking agent of octavinyl polyhedral oligomeric silsesquioxane (OVPOSS). And its properties were compared with conventional hydrogels using N,N′-methylenebisacrylamide (MBA) as cross-linking agent. The copolymers were characterized by Fourier transform infrared spectra and differential scanning calorimetry. The morphology after swelling was presented by scanning electron microscopy. Swelling behaviors in different pH and potential applications in controlled drug delivery of the hydrogels were also examined. The results showed that both hydrogels were pH sensitive. However, as the addition of OVPOSS limited the movement of the molecular chain segment, the swelling ratio and the drug-release rate of theophylline in SGF decreased obviously when using OVPOSS as cross-linking agent, comparing with P(MBA-co-AA) hydrogels. The results in this study suggested that P(OVPOSS-co-AA) could serve as potential candidate for theophylline drug delivery.

Surface functionalization of molybdenum disulfide (MoS2) was prepared by a simple reflux reaction between DITG-MoS2 and octa-vinyl polyhedral oligomeric silsesquioxanes (OvlPOSS). The structure of OvlPOSS-MoS2 was confirmed by XRD, FTIR and TEM. The SEM and TEM results of fracture surface exhibited that OvlPOSS-MoS2 was dispersed well in the matrix due to the good interfacial interaction between the functionalized MoS2 and PVA. The thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) results indicated that the thermal decomposition temperature and the glass transition temperature (Tg) were improved. Compared with pure PVA, the maximum degradation temperature of the PVA/OvlPOSS-MoS2 nanocomposites was increased by 23 °C, and the Tg of the PVA/OvlPOSS-MoS2 was improved by 10.2 °C. Meanwhile, the peak of heat release rate (pHRR) and total heat release (THR) were decreased. The tensile stress was increased by 57% with addition of 2 wt% OvlPOSS-MoS2. Moreover, the addition of OvlPOSS-MoS2 significantly decreased the gaseous products, including hydrocarbons, carbonyl compounds and carbon monoxide, which was attributed to the synergistic effect of OvlPOSS and MoS2: the adsorption and barrier effect of MoS2 inhibited the heat and gas release and promoted the formation of graphitized carbons, while OvlPOSS improved the thermal oxidative resistance of the char layer.

Effect of plasticizer type on the kraft lignin–natural rubber composite microstructure and selected properties was determined. The composites were prepared with addition of a commonly used naphthenic oil plasticizer to study the decomposition product of polyurethane (glycerolysate) and its characteristics. Kraft lignin powder was incorporated into the natural rubber matrix in amounts of 10 and 40 parts per 100 parts of natural rubber (phr). The reference samples were prepared without any lignin present. The chemical interaction between the filler particles and natural rubber macromolecules was analyzed by Fourier transform infrared spectroscopy (FTIR) and the adhesion was characterized by scanning electron microscopy (SEM). The results of the adhesion measurements confirmed poor distribution of lignin particles into the natural rubber matrix with increasing filler content. Optimal lignin content in the composites was 10 phr in the case of both plasticizers. Moreover, the results of FTIR verified the formation of non-covalent bonds and the need for modification of the filler to enhance the reinforcing effect in the natural rubber matrix. Dynamic mechanical analysis (DMA) and mechanical measurements proved that the specimen containing 10 phr of lignin with the use of glycerolysate as plasticizer displayed the highest mechanical performance. It was demonstrated that glycerolysate and naphthenic oil as plasticizing agents showed similar effect on the thermal properties of the prepared composites. Also, the measured mechanical properties, such as tensile strength, hardness, resilience, and abrasiveness confirmed these findings.