How to prepare a hydrogel with high strength and excellent tearing fracture energy is a problem faced by researchers. Here, tough and tear‐resistant double‐network hydrogels (Cx‐SMy gels) are successfully prepared via a facile strategy: micellar polymerization followed by solution polymerization. The strength and fracture energy of these hydrogels are up to 13 MPa and 26500 J m−2, respectively, which are attributed to the synergy of quatra‐crosslinking interactions inside the double‐network. The quatra‐crosslinking interactions include hydrophobic interaction, crystallization, electrostatic attraction, and hydrogen bonding. Moreover, it is confirmed that the facile strategy is a general way to prepare tough hydrogels by using electrolytic monomers and hydrophobic acrylates.
2,2-bis [4-(2-hydroxy-3-methacryloyloxypropoxy) pheny propane (Bis-GMA) and triethylene glycol dimethacrylate (TEGDMA) have been commonly used as a viscous monomer and a reactive diluent in the organic phase of dental restorative composites, respectively. The purpose of addition of TEGDMA is mainly to decrease the high viscosity of Bis-GMA caused by hydrogen bonding between hydroxyl groups. However, some adverse effects will accompany with increased amounts of the TEGDMA, such as higher values of polymerization shrinkage, which is not undesirable for the clinical application. Therefore, substituting hydroxyl groups of Bis-GMA might be an appropriate and effective way to reduce the amount of diluents and weaken the accompanied adverse effects. This work focuses on the synthesis of a novel Bis-GMA derivate, substituting acetyl groups for hydroxyl groups in Bis-GMA. The viscosity of Bis-GMA characterized with rotational rheometer was significantly decreased from 820 Pa.s to 11 Pa.s by substitution of acetyl group, leading to the low amount of TEGDMA in resin matrix. Differential Scanning Calorimeter (DSC) was used for investigating the reaction kinetics of this novel monomer with different mass ratios of TEGDMA. The results suggested that the maximum conversion of the Ac-Bis-GMA can reach 88% while the corresponding value for Bis-GMA is 75%. Dental composites were prepared from 2,2-bis [4-(2-acetyl-3-methacryloyloxypropoxy) pheny propane (Ac-Bis-GMA) or Bis-GMA resin mixtures with TEGDMA filled with 70 wt% silica co-fillers. The results presented that dental composites prepared from new resin matrixes exhibited adequate mechanical properties.
In this work, a starch-water mixture was blended with polyurethane prepolymer (PUP) at 0, 5, 10, 15, and 20 wt% and extruded in a twin screw extruder. The ensuing results showed that the reaction ratio of PUP used for modified starch was 98.6 AE 0.3%. This was attributed to the polyurethane particles being formed under shear stress during extrusion processing. Each polyurethane particle contained many NCO groups with high reaction activity, which therefore increased the reaction probability of PUP micro-particles with starch. The elastic and hydrophobic PUP played an important role in improving the properties of modified starch. SEM showed that the starch and polyurethane had good compatibility; the toughness, hydrophobicity, and thermal stability of modified starch thus sharply improved. This work provided a method for the preparation of high reaction efficiency modified starch.
Modified thermoplastic starches (TPS) were successfully prepared from corn starch (CS) and hydrophobic polyurethane prepolymers (PUPs) by solid‐state reactions under intensive mixing conditions. The structure and properties were investigated using FTIR, SEM, wide‐angle XRD, tensile testing machine, Brookfield viscometer, and contact angle (CA) meter. The results showed that 98.6 ± 0.4% of PUP was cross‐linked to starch, suggesting a high efficiency of the solid‐state reaction. Compared with unmodified starch, the hydrophobic property of the modified TPS was improved, resulting in an increase of the CAs and a decrease of the Brookfield viscosity. Morphology analysis indicated that the modified starch exhibited increased compatibility between the PUP particle and nature starch, leading to the increased elongation at break.
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