Structural transition of nanogel star polymers with pH by controlling PEGMA interactions with acid or base copolymers

Abstract

We use small angle x-ray scattering (SAXS) to characterize a class of star diblock polymers with a nanogel core on which the outer block arms are comprised of random co-polymers of temperature sensitive PEGMA with pH sensitive basic (PDMAEMA) and acidic (PMAA) monomers. The acquired SAXS data shows that many of the nanogel star polymers undergo a sharp structural transition over a narrow range of pH, but with unexpectedly large shifts in the apparent pKa with respect to that of the acidic or basic monomer unit, the linear polymer form, or even an alternate star polymer with a tightly cross-linked core chemistry. We have demonstrated a distinct and quantifiable structural response for the nanogel star copolymers by altering the core or by pairing the monomers PDMAEMA-PEGMA and PMAA-PEGMA to achieve structural transitions that have typically been observed in stars through changes in arm length and number.

pH-Responsive Saloplastics Based on Weak Polyelectrolytes: From Molecular Processes to Material Scale Properties

“…However, current approaches present several drawbacks, including the need to perform an additional purification step to separate the cation/carboxylate complexes formed from the clean water . In addition, the apparent p K a of materials containing high concentrations of carboxylic moieties is typically increased, , which shifts the optimum operating pH for water purification to values higher than pH 5.5–6. , Since transition metal cations like Ni 2+ and Cu 2+ tend to form hydroxide in these conditions, sorption materials efficient at acidic pH need to be developed. The COPEC approach offers a simple route for elaborating sorbent materials that can be processed into membranes, fibers, and powders, ultimately allowing a direct separation from clean water.…”

Effect of Hydrophobic Core Topology and Composition on the Structure and Kinetics of Star Polymers: A Molecular Dynamics Study

“…In our previous studies, ,, the hydrophobic domain was found to form a highly collapsed, glassy, impenetrable, and essentially spherical core around the adamantane center. The star polymers previously simulated were also highly symmetric as constructed.…”

“…15 Differences in local density from linear analogs have also been shown to affect responsiveness to physiological factors such as temperature, ion concentration, and pH. 16 In our previous studies, 13,14,17 the hydrophobic domain was found to form a highly collapsed, glassy, impenetrable, and essentially spherical core around the adamantane center. The star polymers previously simulated were also highly symmetric as constructed.…”

Thermoresponsive Nanogels Based on Different Polymeric Moieties for Biomedical Applications

“…The LCSTs of PEG-based polymers can be regulated by copolymerization with hydrophobic units [ 142 ]. Hydrophobic units like methyl and ethyl groups can regulate the polarity and temperature-responsiveness of the polymer within a physiological temperature range [ 143 ]. The composition of the monomers, molecular weight, concentration, and ionic strength of the solution considerably affect the LCST of PEG-based copolymers [ 144 ].…”