Purpose: Soluplus® is a PVAc-PVCap-PEG graft solid amphiphilic copolymer that is frequently researched for its uses as an excipient in solid dosage forms and as a dissolution and solubility enhancer to promote fast drug release. Vitamin E, a hydrophobic viscous liquid, acts as an important fat-soluble antioxidant and anti-inflammatory agent that is contained in many cosmetic products. We discovered that soluplus can be dissolved in vitamin E under heat at loadings up to ~40% by weight of the blend. The resultant product is a tacky and highly adhesive material. The objective of this work was to evaluate the rheological, adhesive, and texture properties of the soluplus-vitamin E blends for potential use in the future development of pressure sensitive adhesives and adhesive patches.
Methods: Soluplus was dissolved in vitamin E at increasing concentrations from 0 to 40% by weight under heat (~100oC). The flow behavior of the soluplus-vitamin E blends was determined by applying shear stress using an advanced AR2000 rheometer. Under the linear viscoelastic region (LVR), the rheological properties of the blends such as dynamic viscosity (η’), storage modulus (G'), loss modulus (G"), and tangent of the phase angle (tan δ) were measured. Also, the hardness, adhesiveness, and cohesiveness of the blends was measured by the TA.XT plus texture analyzer.
Results: Rheological analysis showed that the viscosity of the soluplus-vitamin E blends increased from 4.375 to 9397 Pa.s by increasing the concentration of soluplus from 0 to 40% by weight in the blend. This viscosity was temperature dependent where viscosity decreased as the temperature increased from 20 to 90°C. The adhesiveness of the soluplus-vitamin E also increased from 0.016 to 17.63 Kg/s. At these values, and depending on soluplus load, the soluplus-vitamin E blends had similar or higher adhesiveness than commercial acrylic DURO-TAK pressure-sensitive adhesives that are commonly used in pharmaceutical applications.
Conclusion: The adhesive, rheological, and mechanical properties of the soluplus-vitamin E viscous blends can be manipulated by adjusting the ratio of the two ingredients. The results from this study also indicated that vitamin E based materials have great potential to be used as adhesives and dressings in topical applications. They may also present opportunities in other applications that were beyond the scope of the present work.