Self-Assembly Assisted Polypolymerization (SAAP) of Diblock Copolymer Chains with Two Reactive Groups at Its Insoluble End

Abstract

Preparation of diblock copolymers, (≡,N3)-poly(N-isopropylacrylamide)-b-poly(N,N-dimethylacrylamide) [(≡,N3)-PNIPAM-b-PDMA] and (≡,N3)-polystyrene-b-PNIPAM [(≡,N3)-PS-b-PNIPAM], with reactive alkyne and azide at one end using a trifunctional agent enables us to study how their self-assembly in a selective solvent affects interchain coupling, i.e., the self-assembly assisted polypolymerization (SAAP). As expected, (≡,N3)-PNIPAM-b-PDMA chains self-assemble into a micelle-like core–shell structure with a PNIPAM core in water at 50 °C. The coupling of as many as 17 PNIAPM ends together led to star-like chains, independent of the copolymer concentration, while the coupling efficiencies at lower temperatures (with no self-assembly) and in good solvents are much lower. These star-like chains remember their “birth” state in water and undergo the intrachain contraction to form single-chain micelles instead of large multichain aggregates. On the other hand, (≡,N3)-PS-b-PNIPAM exists as individual chains in THF, a mixture of unimers and micelles in 2-propanol, the core–shell micelles in methanol, and irregular aggregates in water. Only in methanol, the coupling efficiency is notably improved. The addition of water into 2-propanol enhances the self-assembly and so does the interchain coupling. The current study shows that even the solvophobic interaction makes the insoluble blocks less mobile inside the core and decreases the collision probability of reactive chain ends, the self-assembly still concentrates the reactive ends together and assists the coupling if the selective solvent is properly chosen.

Synthesis and properties of antifouling poly(CL-co-zDMAEMA) zwitterionic copolymer by one-step hybrid copolymerization

“…The hydrodynamic radius (bR h N) of micelles and its distribution were calculated from the autocorrelation functions using the CONTIN algorithm [26]. As shown in Fig.…”

“…Self-assembly micelles with hydrophilic shells and hydrophobic cores have received much attention as potential drug carriers in recent years [26,32]. Therefore the solubilization capacity of these amphiphilic copolymers in water was studied using pyrene as a model compound.…”

“…As shown in Fig. 9, there are two characteristic absorption peaks located at 324 and 340 nm for the typical UV-vis spectra of pyrene solutions, which are not interfered by the absorption bands of PCL and PDMAEMA [26,32,34,35]. The spectrum of copolymer solution with a concentration higher than 0.20 mg/mL is not measured because of testing accuracy above 2.0.…”

“…three Waters Styragel columns (HT2, HT4, HT6), respectively, equipped with a refractive index detector (RI, Wyatt WREX-02, using a conventional calibration with linear polystyrene standards) [20,26]. Differential scanning calorimetry (DSC) was measured on a DSC Q2000 in dry N 2 atmosphere.…”

“…The time correlation functions were analyzed by both the cumulant and CONTIN analyses. The details of LLS instrumentation and theories have been described elsewhere [26].…”