OEG-based Thermoresponsive Comb-like Dendronized Polymers And Their Use As Colorimetic Sensors

Thermoresponsive polymers are attractive in various areas ranging from sensorsto bio-related applications, and have received significant interest in last decades. Todevelop a polymer with fast and sharp transitions, as well as bio-compatibility is oneof most interesting topics in polymer chemistry. Numerous studies show that,dendronized polymers which concept with the key units oligoethylene glycol-basedthree-folded dendrons show unique phase transitions in the temperature range of30-64oC. On the basis of previous studies, here two kinds of comb-like dendronizedpolymers (PG1(A) and PG1(G)) with either hydrophobic alkyl chain or hydrophilicoligoethylene glycol chain bridged between the polymer main chain and dendron sidegroups were efficiently synthesized via macromonomer route. Interestingly, thesepolymers show fast and sharp phase transitions with small hysteresis, and the morehydrophobic polymer PG1(A) could form denser aggregates than the morehydrophilic polymer PG1(G).In addition, by copolymerization with monomer bearing solvatochromic dye[disperse Red1(DR1)], two novel polymer-based colorimetric sensorsPG1(A)-co-DR1and PG1(G)-co-DR1were prepared. Their aqueous solutions areclear in different color at room temperature. When increasing the temperature upontheir LCST, the solutions change to turbid together with obvious color change at pH=1and negligible color change at pH=7. These copolymers could be used as uniquesensors for detecting the temperature and pH of microenvironment.Encouraged by above results, three colorimetric sensors based on either first orsecond generation dendronized polymers were prepared through the same strategy asthe comb-like dendronized polymeric sensors. They exhibit differentthermoresponsive behaviors due to their varied structures, thus, can be used as sensorsfor different microenvironment detection.