Pr. Melissa GRUNLAN and Dr. Jaime GRUNLAN from Texas A&M will give 2 seminars @IRDL Smart Plastics Group room CR204 on the 13th of June 2022 at 3pm. See Lectures abstracts below:
Self-fitting, Shape Memory Polymer Scaffolds for Bone Defect Repair
Abstract: Shape memory polymer (SMP) scaffolds were prepared having the capacity to conformally “self-fit” into irregular bone defects. Initially, porous scaffolds were fabricated via photo crosslinking of linear-poly(ε-caprolactone) (PCL) diacrylate using a solvent casting/particulate leaching (SCPL) method employing a fused salt template. Following exposure to warm saline at T > Ttrans (Ttrans = ~Tm of PCL), the scaffold became malleable and could be pressed into an irregular model defect. Subsequent cooling caused the scaffold to lock in its temporary shape within the defect. However, a linear-PCL-DA self-fitting scaffold is limited by a slow degradation rate as well as a high “fitting temperature” (Tfit = Tm of PCL ~55 ºC) required for press-fitting that may reduce tissue safety. Thus, we have developed scaffolds based on semi-interpenetrating network (semi-IPN) scaffolds comprised of crosslinked PCL and thermoplastic poly(L-lactic acid) (PLLA), each with a linear or star architecture. Semi-IPN scaffolds prepared with the star-PCL macromer exhibited the desired reduction in Ttrans to ~45 ºC. Those based on star-PCL and star-PLLA had a favorable combination of increased radial expansion force, accelerated degradation, and reduced solution viscosity useful for scaffold fabrication.
Water-Based Protective Nanocoatings from Polyelectrolytes: Flame Retardancy, Super Gas Barrier, and Heat Shielding
Abstract: Layer-by-layer (LbL) assembly is a conformal coating “platform” technology capable of imparting a multiplicity of functionalities on nearly any type of surface in a relatively environmentally friendly way. At its core, LbL is a solution deposition technique in which layers of cationic and anionic materials (e.g. nanoparticles, polymers and even biological molecules) are built up via electrostatic attractions in an alternating fashion, while controlling process variables such as pH, coating time, and concentration. Here we are producing nanocomposite multilayers (50 – 1000 nm thick), having 10 – 96 wt% clay, that can be completely transparent, stop gas permeation, and impart extreme heat shielding to polymeric substrates. In an effort to impart flame retardant behavior to fabric using fewer processing steps, a water-soluble polyelectrolyte complex (PEC) was developed. This nanocoating is comprised of polyethylenimine and poly(sodium phosphate) and imparts self-extinguishing behavior to cotton fabric in just a single coating step. Adding a melamine solution to the coating procedure as a second step renders nylon-cotton blends self-extinguishing. More recently, a PEC coating was developed for polyester-cotton. It passes vertical flame testing after five standard washes or 8 hours in boiling water. Either of these two coating techniques can be deposited using flexographic printing or spray-coating tools. Opportunities and challenges will be discussed. Our work in these areas has been highlighted in C&EN, ScienceNews, Nature, Smithsonian Magazine, Chemistry World and various scientific news outlets worldwide. For more information, please visit my website: http://nanocomposites.tamu.edu