Mechanical and Thermal Evaluation of Carrageenan/Hydroxypropyl Methyl Cellulose Biocomposite Incorporated with Modified Starch Corroborated by Molecular Interaction Recognition

Abstract

Vegetarian hard capsule has attracted surging demand as an alternative to gelatin; however, only few have been commercialized. Carrageenan extracted from seaweed has the potential to be utilized as a hard capsule material. Improving the mechanical and thermal properties of carrageenan biocomposite is therefore of great importance for future use in the drug delivery system. Hence, carboxymethyl sago starch (CMSS) was incorporated to strengthen the carrageenan biocomposite in a concentration range from 0 to 1.0% w/v. The intermolecular hydrogen bonding formed between carrageenan and CMSS was revealed via density functional theory (DFT) calculations and substantiated by 1 H NMR and FTIR spectra. The result showed that the hydrogen bond is established between hydroxyl (carrageenan)−carbonyl (CMSS) groups at a distance of 1.87 Å. The bond formation subsequently increased the tensile strength of the biocomposite film and the loop strength of the hard capsule by 20.6 and 7.7%, respectively. The glass transition temperature of the film was increased from 37.8 to 47.8 °C, increasing the thermal stability. The activation energy upon decomposition of the film is 74.4 kJ•mol −1 , representing a 26.2% increase over the control carrageenan. These findings demonstrate that incorporation of CMSS increases the properties of carrageenan biocomposite and provides a promising alternative to animal-based hard capsules.

Influence of Polar Protic Solvents on Urea Morphology: A Combination of Experimental and Molecular Modeling

“…The DFT calculations of the optimized structures were carried out using the Gaussian 09W program package by determining the single-point energies and harmonic frequencies. The DFT calculations were carried out using Becke’s three parameters combined with the Lee, Yang, and Parr (B3LYP) correlation functionals with a 6-31G (d,p) base set . Single-point energy calculations were executed to generate Mulliken atomic charges, q, and the electrostatic potential (ESP) surface map of the optimized structures.…”

“…The DFT calculations were carried out using Becke's three parameters combined with the Lee, Yang, and Parr (B3LYP) correlation functionals with a 6-31G (d,p) base set. 40 Singlepoint energy calculations were executed to generate Mulliken atomic charges, q, and the electrostatic potential (ESP) surface map of the optimized structures. The harmonic frequency calculations were conducted to determine the total energy of the minimized structures at standard ambient temperatures and pressures.…”