Topology and Molecular Architecture of Polyelectrolytes Determine Their pH-Responsiveness When Assembled on Surfaces

Abstract

Polymer composition and topology of surface-grafted polyacids determine the amplitude of their pH-induced swelling transition. The intrinsic steric constraints characterizing cyclic poly­(2-carboxypropyl-2-oxazoline) (c-PCPOXA) and poly­(2-carboxyethyl-2-oxazoline) (c-PCEOXA) forming brushes on Au surfaces induce an enhancement in repulsive interactions between charged polymer segments upon deprotonation, leading to an amplified expansion and a significant increment in swelling with respect to their linear analogues of similar molar mass. On the other hand, it is the composition of polyacid grafts that governs their hydration in both undissociated and ionized forms, determining the degree of swelling during their pH-induced transition.

Macrocyclization efficiency for poly(2-oxazoline)s and poly(2-oxazine)s

“…Interestingly, these new signals differ between PnPropOx 20 and PnPropOzi 20 . In agreement with data from previous studies, 1,9,11 CuAAC of PnPropOx 20 results in a distinct signal group between 4.50 and 4.60 ppm. However, CuAAC of PnPropOzi 20 results in a broader signal group between 4.30 and 4.70 ppm.…”

“…6 However, applicability of these materials remains limited by a number of synthetic challenges. 7 Cyclic polymers are commonly synthesized from linear, heterotelechelic precursors, 2,8,9 which undergo intramolecular ring closure under high dilutions to avoid inter-molecular linkages. Whilst effective, an inherent challenge is the interdependency of reaction parameters such as solvent, batch volume, and reagents, which dictate the cyclization efficiency, making optimization on a case-by-case basis necessary.…”

“…Subsequently, CuAAC was performed on the polymers using copper( i ) bromide and N , N , N ′, N ′′, N ′′-pentamethyldiethylenetriamine (PMDTA) in dichloromethane (DCM) to yield either monocyclic polymers or higher molecular weight by-products (Scheme 1, B). These reaction conditions are typical for cyclization reactions, 2,3,9,10 as the Cu( i )/PMDTA complex stabilizes the Cu( i ) oxidation state, 24 while DCM as a non-coordinating solvent enhances reaction kinetics. 25 To optimize reaction conditions, batch volume and Cu( i )Br/PMDTA catalyst amount were varied.…”

Zwitterionic Poly(carboxybetaine) Brush/Albumin Conjugate Films: Structure and Lubricity

“…The liquid infusion and confinement in the proteoglycan layer at the sliding interface are considered an important aspect of the induction of fluid lubrication . Numerous artificial composite materials that mimic the hierarchical structure of the cartilages have been proposed. , As a macromolecular system that mimics the articular cartilages, polymer brushes with hydrophilic polymer chains have been investigated, and the excellent lubricating performance has been demonstrated in a huge number of reports in the past. − In particular, charged polymer chains including polyelectrolytes and zwitterionic polymers exhibit outstanding lubrication performance in wet conditions. The electrostatic long-range repulsive forces and/or strong hydration are attributed to the enormous lubrication.…”

Ionic Effect on Electrochemical Behavior of Water-Soluble Radical Polyelectrolytes

“…11 Polyelectrolytes are generally water-soluble, forming charged polymer chains surrounded by dissociated counterions. 12,13 In many cases, their chain conformations and charge states vary with pH, 14 ionic strength, 15 and electrostatic interactions. 16 One interesting behavior of polyelectrolytes is their movement driven by an external electric field, which is the basis of the well-known gel electrophoresis techniques for analyzing charged biopolymers, such as DNA and proteins.…”