skip to main content

Title: Effect of Water on the Thermal Transition Observed in Poly(allylamine hydrochloride)–Poly(acrylic acid) Complexes
Author(s) / Creator(s):
; ; ;  ;
Publisher / Repository:
American Chemical Society
Date Published:
Journal Name:
Page Range / eLocation ID:
7563 to 7570
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Charge densities of cationic polymers adsorbed to lipid bilayers are estimated from second harmonic generation (SHG) spectroscopy and quartz crystal microbalance with dissipation monitoring (QCM-D) measurements. The systems surveyed included poly(vinylamine hydrochloride) (PVAm), poly(diallyldimethylammonium chloride) (PDADMAC), poly- l -lysine (PLL), and poly- l -arginine (PLR), as well as polyalcohol controls. Upon accounting for the number of positive charges associated with each polyelectrolyte, the binding constants and apparent free energies of adsorption as estimated from SHG data are comparable despite differences in molecular masses and molecular structure, with Δ G ads values of −61 ± 2, −58 ± 2, −57 ± 1, −52 ± 2, −52 ± 1 kJ mol −1 for PDADMAC 400 , PDADMAC 100 , PVAm, PLL, and PLR, respectively. Moreover, we find charge densities for polymer adlayers of approximately 0.3 C m −2 for poly(diallyldimethylammonium chloride) while those of poly(vinylamine) hydrochloride, poly- l -lysine, and poly- l -arginine are approximately 0.2 C m −2 . Time-dependent studies indicate that polycation adsorption to supported lipid bilayers is only partially reversible for most of the polymers explored. Poly(diallyldimethylammonium chloride) does not demonstrate reversible binding even over long timescales (>8 hours). 
    more » « less
  2. null (Ed.)
  3. Abstract We report the thermoresponsive assembly and rheology of an amphiphilic thermosensitive graft copolymer, poly(ethylene glycol)-graft-(poly(vinyl caprolactam)- co -poly(vinyl acetate)) (commercial name Soluplus ® ), which has been investigated for potential biomedical applications. It has received attention due to is ability to solubilize hydrophobic drugs and for its thickening behavior close to body temperature. Through use of the synchrotron at Brookhaven National Lab, and collaboration with the department of energy, the nanoscale structure and properties can be probed in greater detail. Soluplus ® undergoes two structural changes as temperature is increased; the first, a concentration independent change where samples become turbid at 32 °C. Increasing the temperature further causes the formation of physically associated hydrogels. This sol-gel transition is concentration dependent and occurs at 32 °C for 40 wt% samples, and increases to 42 °C for 10 wt% samples. From variable temperature SAXS characterization micelles of 20–25 nm in radius can be seen and maintain their size and packing below 32 °C. A gradual increase in the aggregation of micelles corresponding to a thickening of the material is also observed. Close to and above the gelation temperature, micelles collapse and form a physically associated 3D network. A model is proposed to explain these physical effects, where the poly(vinyl caprolactam) group transitions from the hydrophilic corona at room temperature to the hydrophobic core as temperature is increased. 
    more » « less