Multi-stimuli responsive poly(N-isopropyl-co-tetraphenylethene) acrylamide copolymer mediating AIEgens by controllable tannic acid

• Published in: Polymer (Guilford) 2022-05, Vol.249, p.124824, Article 124824
• Main Authors: Iqbal, Shahzad, Ahmed, Farid, Wang, Ziyan, Xu, Weiqing, Zeng, Yating, Xiong, Hai
• Format: Article
• Language: English
• Subjects: Acrylamide; AIE; Aqueous solutions; Copolymerization; Copolymers; Drug delivery; Drug delivery systems; Fluorescence; Isopropylacrylamide; Light scattering; Monomers; p-NIPAM; pH effects; pH-responsive; Photon correlation spectroscopy; Poly-N-isopropylacrylamide; Stimuli; Tannic acid; Temperature effects; Temperature-responsive
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2022.124824

Copolymerization of N-isopropylacrylamide (NIPAM) and tetraphenylethene (TPE) acrylamide monomers produced aggregation-induced emission (AIE) active copolymers P1, P2, and P3 with relatively lower molecular weights (6000). Like poly-N-isopropylacrylamide (p-NIPAM), an aqueous solution of copolymers (P1-P3) responds to temperature and undergoes a change in fluorescence intensity due to conformational transition (swelling/shrinking) below and above their lower critical solution temperature (LCST), respectively. The LCST of p-NIPAM (32 °C) shifted downward upon the incorporation of TPE in the copolymer chains depending on the concentration of TPE. Compared to P1, the fluorescence response increased to a five-fold enhancement with increasing concentrations of tannic acid (TA) owe to the form of the P1-TA complex. Furthermore, the P1-TA complex showed a surprising change in fluorescence response under the effect of temperature and pH value. The conformational transitions of P1-TA were also studied by dynamic light scattering (DLS). DLS measurements for the P1-TA complex justified its fluorescence response based on particle size at different concentrations and pH value. Such stimuli-responsive AIE-active copolymers find potential applications in drug delivery systems for monitoring loading and release processes by fluorescence. [Display omitted] •Compared to P1, the fluorescence intensity of AIE-active P1-TA complex increased to a five-fold enhancement.•A multi-stimuli response on temperature and pH value based on intermolecular hydrogen bonding interaction.•The interpenetrating networks can be formed without using two polymer chains or more.