Impact of cyclization and dendronization on multi-tunable thermoresponsive behaviors of polyacrylamide copolymers

Abstract

Two pairs of linear and cyclic polyacrylamide-type thermoresponsive heterofunctional-dendron-bearing polymers (THDPs) are designed to achieve on-demand phase transitions and nanostructures.

Multi-tunable thermoresponsive behaviors of poly(amido thioether)s

“…Owing to the formation of interchain amide–amide HBs with electron delocalization, the elevated chain rigidity favored the n–π* transition of carbonyl groups to present an emission at about 440 nm. 24,25,57–62 Other fluorescence bands were proposed to primarily originate from the emissions related to amide–water HBs ( λ em = 373 nm), amide–imidazolyl/diethylamino HBs ( λ em = 392 nm), and intrachain amide–amide HBs ( λ em ≈ 413 nm). The maximal emissions of P3 and P4 solutions appeared at 439 nm, while the maximal emissions of other polymer solutions related to amide–amide HBs ranged between 413 and 439 nm due to the overlapping of emission bands related to inter/intrachain HBs.…”

“…, pH, redox and light irradiation) are incorporated into TRPs, stimuli-induced changes in structural arrangements or chemical compositions can efficiently regulate the temperature and/or type of phase transition. 19–25 To precisely modulate thermoresponsive behaviors, hydrogen bonding and other interactions can be subtly combined to achieve the synergistic effect, and rational macromolecular design endows TRPs with single, dual and even triple thermoresponsiveness in water, alcohol or other media. 7,12,13,20–34 Despite tremendous progress, the research progress in UCST polymers lags far behind that of LCST polymers.…”

“…19–25 To precisely modulate thermoresponsive behaviors, hydrogen bonding and other interactions can be subtly combined to achieve the synergistic effect, and rational macromolecular design endows TRPs with single, dual and even triple thermoresponsiveness in water, alcohol or other media. 7,12,13,20–34 Despite tremendous progress, the research progress in UCST polymers lags far behind that of LCST polymers. To date, the types of UCST polymers have been relatively limited, and UCST polymers with cloud points close to the physiological temperature have been scarcely revealed.…”

“…Compared with chain polymerization to synthesize most of the TRPs with an inert carbon–carbon backbone, stepwise polymerization can lead to the formation of a backbone with more flexible compositions and functions. By virtue of tandem amine–thiol–ene reactions, the pendant thiolactone groups of a presynthesized polymer can be readily converted to heterofunctional Y junctions, 22–25 and bi/multicomponent polymerization using thiolactone-bearing monomers allows the formation of linear or hyperbranched poly(amido thioether)s (PATEs). 40–43 For instance, starting from N -acryloylhomocysteine thiolactone (ATL), we have adopted one-pot thiol–amine–acrylamide polyaddition to prepare hydroxyethyl- and diethylamino-bearing multi-responsive tricomponent PATEs, 43 and polymer aqueous solutions can shift from LCST ( f OH < 0.84) to LCST–UCST ( f OH = 0.84–0.89) and UCST ( f OH > 0.89) with increasing hydroxyl fraction ( f OH ) in comonomer units.…”

“…Some methods are efficiently combined to systematically reveal the thermoresponsivity of polymer solutions under different conditions, in which turbidimetry is used to gain insight into LCST/UCST behavior via monitoring variations of transmittances, 1 H NMR analysis is beneficial for understanding the status of solvation of subunits, the combination of dynamic laser scattering (DLS) and TEM analyses favors the revealing of thermally induced aggregation/disassociation of polymer assemblies, and fluorometry enables the analysis of variable inter/intrachain hydrogen bonding via measuring the fluorescence intensity. The feature of non-traditional intrinsic luminescence (NTIL) of amide-bearing polymers 24,25,57–62 allows monitoring variations of amide-related hydrogen bonding upon heating. The types and temperatures of LCST/UCST-type phase transitions can be rationally tuned by controlling inherent and external factors.…”