Phase Separation and pH-Dependent Behavior of Four-Arm Star-Shaped Porphyrin-PNIPAM4 Conjugates

Nadiia Velychkivska

doi:10.1021/acs.macromol.1c02188

Phase Separation and pH-Dependent Behavior of Four-Arm Star-Shaped Porphyrin-PNIPAM4 Conjugates

2022-03-04

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DOI：10.1021/acs.macromol.1c02188

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Star-shaped porphyrin-PNIPAM(4) (PP) conjugates having four PNIPAM arms connected to a central tetraphenylporphyrin unit were synthesized using reversible addition-fragmentation chain-transfer polymerization. Temperature-induced phase-separation behavior of the conjugates was investigated, and the lower critical solution temperature (type II)-composition phase diagram was constructed using Flory-Huggins theory. Interestingly, in contrast to PNIPAM homopolymers, the shorter PNIPAM arms of PP conjugates lead to a lower phase-separation temperature (T-p). The concentration dependency of the size of the cooperative domain was also determined. Below T-p, experimental data indicate that PP behaves as a 1D supramolecular polymer with a concentration-dependent length, while above T-p, PP globules adopt a larger spherical shape. Various temperature- pH reversible and irreversible interdependencies (cross-effects) between phase separation and protonation were observed. The PP conjugates represent a dual temperature-pH-responsive model system possessing various aggregated states, making them candidates for visual indicators, pH or temperature sensors, or singlet oxygen generators for biomedical applications.

Keywords:

ZERO CRITICAL CONCENTRATIONS

COIL-GLOBULE TRANSITION

PORPHYRIN-CORE

POLY(VINYL METHYL-ETHER)

POLYDISPERSE POLYMERS

COLLOIDAL STABILITY

SWELLING BEHAVIOR

AQUEOUS-SOLUTIONS

BLOCK-COPOLYMERS

TEMPERATURE

Phase Separation and pH-Dependent Behavior of Four-Arm Star-Shaped Porphyrin-PNIPAM4 Conjugates

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