Novel thermosensitive telechelic PEGs with antioxidant activity: synthesis, molecular properties and conformational behaviour

Abstract

We report on the synthesis and solution properties of novel tailor -made polymer conjugates, which are highly compelling for biomedical applications due to their antioxidant activity and the potential to fine-tune their thermosensitive properties. These conjugates consist of polyethylene glycol (PEG polymers containing antioxidant moieties, namely 3 -(3,5-di-tertbutyl-4-hydroxyphenyl)propionate or 2-benzamido-3-(3,5-di-tert-butyl-4-hydroxyphenyl)acrylate, as end groups that differ in activity and hydrophobicity. It was shown that all of the synthesised conjugates have low critical solution temperatures (LCSTs) characteristic of type II polymers on a phase diagram. By simply varying the PEG molecular weight, the solution properties, including the LCST value, could be easily tuned across a broad temperature range of 20-90 ºC, providing an ideal method for the creation of thermosensitive polymers. It was also established that the LCST value and the polymer conjugate conformation depend on the antioxidant structure. From dynamic light scattering and small-angle X-ray scattering data, we were able to construct a complete sequence diagram of the conformational phase behaviour for the polymers with increasing temperature. It was observed that the conjugate conformation changes are the result of water shifting from a thermodynamically favourable solvent to an unfavourable one. This process then leads to compaction of the conjugate, followed by its aggregation.

Synthesis and solution properties of a temperature-responsive PNIPAM–b-PDMS–b-PNIPAM triblock copolymer

“…The ability to reduce CPT by introducing a hydrophobic moiety has been reported previously for a variety of copolymers. [42][43][44] The incorporation of hydrophilic PEG as a central block creates an opposing trenda CPT value that increases, as was previously observed for PNIPAM-b-PEG-b-PNIPAM copolymer. 27 Calculated intensity weighted distribution functions of the hydrodynamic radius Rh show a bimodal distribution at 25 °C and a monomodal distribution at 40 °C (Figure 2b, inset).…”

BioSAXS Sample Changer: a robotic sample changer for rapid and reliable high-throughput X-ray solution scattering experiments

“…The sample changer is particularly helpful for projects that require the measurement of large numbers of samples under varying conditions. An example can be found in Sergeeva et al (2014), where the authors studied the solution properties of several tailor-made polyethylene glycol polymers with antioxidant moieties at different concentrations and temperatures. The high-throughput and extensive screening possibilities offered by the Sample Changer permitted full automation of the measurements and the rapid extraction of phase diagrams of the polymers.…”

Smart polymers in drug delivery systems on crossroads: Which way deserves following?

“…Hydrophobic comonomers favorable to segment-segment interactions in polymer tend to decrease the LCST, whereas hydrophilic comonomers favorable to segment-solvent interactions have the opposite effect [84,85]. Triblock copolymers MeOX-(iPrOX-co-BuOx)-MeOX with thermoresponsive properties were reported by Hruby et al [40] It was found that as the temperature increases, the polymers transform from single molecules to loose aggregates to compact nanoparticles.…”