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The focus of this work was on the significant changes in the water dynamics of aqueous poly(N-isopropylacrylamide) (PNIPAM) solution during sol-to-gel transition. Through the use of NMR (particularly two-dimensional 2 H NMR T 1-T 2 relaxation) and rheology, we were able to show that below 34 o C fast exchange occurs among free water and water molecules adsorbed on the surface of PNIPAM molecules. At 34 o C, PNIPAM becomes aggregated; most of the water molecules are trapped in the PNIPAM aggregates, where water molecules with different dynamics are found. Above 34 o C, PNIPAM molecules aggregate further to form a gel network; the free bulk water then becomes dominant at this stage. On the basis of these observations, a model where water molecules interact with PNIPAM in different ways during the transition was proposed. We believe that our experimental approach provides new information and fresh perspectives on the sol-to-gel transition of PNIPAM.

There is current interest in using biobased materials to produce food packaging that can increase the shelf-lives of fruits and vegetables and minimize food spoilage in supermarkets and at the same time not generating plastic waste that causes long-term disposal problems. A good candidate for such materials is the polysaccharide, such as carboxymethyl cellulose (CMC), which is edible and biodegradable. In this work films were produced from two CMC materials with different degrees of substitution (DS) that encapsulated four different essential oils (eugenol, rosemary oil, coriander oil, and nutmeg oil) that are known to have beneficial properties for food applications. The mechanical properties, opacity, and water vapor permeation were evaluated. In general, the essential oil-embedded CMC with the two DS values behaved rather differently. In particular, the essential oil-embedded CMC with 0.7 DS degree of substitution gave stronger and more flexible films and may be more suited for use in food packaging.

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Nonwoven fabrics have grown in popularity in recent years due to their overwhelming usage in a wide range of consumer products. Cotton-based nonwovens are of particular interest because of their ability to be recycled and reused, resulting in a more environmentally friendly product compared to their petroleum-based counterparts. The current research characterized the use of cottonseed protein as an additive to increase the dry strength of cotton-based nonwovens. The tensile strength of nonwovens was found to increase as the concentration of protein applied was increased. At 11% protein concentration, the tear strength and burst strength increased significantly (relative to the nonwoven by itself) by 288% (machine direction) and 295%, respectively. Further characterization by thermogravimetric analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy suggested that cottonseed protein interacted with the cotton fiber in the nonwoven fabric to produce the increased dry strength.