Dispersion RAFT polymerization: comparison between the monofunctional and bifunctional macromolecular RAFT agents

Abstract

The dispersion RAFT polymerizations mediated with monofunctional and bifunctional macro-RAFT agents were comparatively studied, in which different block copolymer morphologies were detected.

Macro-RAFT agent mediated dispersion polymerization: the monomer concentration effect on the morphology of the in situ synthesized block copolymer nano-objects

“…55 From the 1 H NMR spectra shown in Figure 1B, all the proton signals are nicely assigned, and therefore the chemical structure of PEG 45 -TTC is confirmed. By comparing the signals at 1.10-1.45 ppm (b) and at 3.61-3.70 ppm (g), the molecular weight M n,NMR of PEG 45 -TTC at 2.3 kg/mol is obtained.…”

“…By carefully checking the entrant in the vesicles, four entrapped vesicles of 1, 2, 3 and 4 as shown by the high-resolution TEM images are classified. In the general macro-RAFT agent mediated dispersion RAFT polymerization at low or moderate monomer conversion, the morphology evolution from nanospheres to worms and finally to vesicles have been found, [47][48][49][50][51][52][53][54][55][56][57][58][59][60] and the reason is ascribed to the increasing interfacial curvature between the solvophilic and solvophobic blocks with the extension of the solvophobic block during the RAFT polymerization. Clearly, the present PEG 45 -TTC macro-RAFT agent mediated dispersion polymerization at high monomer concentration affords new morphology of the PEG-b-PS diblock copolymer including the porous nanospheres, the bicontinuous nanospheres and the entrapped vesicles, which is much different from the dispersion RAFT polymerization under low or moderate monomer concentration.…”

“…First, the polymerization degree (DP) of the solvophobic block is found to be firmly correlative to the morphology of the in situ synthesized block copolymer nanoobjects, and the morphology of the block copolymer nanoobjects usually undergoes the transition from nanospheres to worms and finally to vesicles with the increasing DP of the solvophobic block during the dispersion RAFT polymerization. [47][48][49][50][51][52][53][54][55][56][57][58][59][60] Second, the chain length of the macro-RAFT agent, which forms the solvophilic block of the in situ synthesized block copolymer, also exerts great influence on the morphology of the block copolymer nano-objects. [52][53][54][55][56][57][58] It is found that, the long macro-RAFT agent leads favorably to block copolymer nanospheres and the short macro-RAFT agent leads favorably to block copolymer vesicles.…”

“…46,[56][57][58] By tuning the aforementioned parameters, block copolymer nano-objects with various morphologies such as nanospheres, nanorods, nanowires, and vesicles were prepared through dispersion RAFT polymerization. [47][48][49][50][51][52][53][54][55][56][57][58][59][60] Compared with the numerous reports on the block copolymer composition affecting the morphology of the block copolymer nano-objects, [47][48][49][50][51][52][53][54][55][56][57][58][59][60] the monomer concentration affecting the morphology of the in situ synthesized block copolymer nano-objects during the dispersion RAFT polymerization is inappropriately neglected, 56,57 although it is revealed that some interesting block copolymer morphologies such as multi-layered vesicles has been prepared at 50 wt% concentrated monomer concentration under dispersion condition. 44 In this study, the poly(ethylene glycol) trithiocarbonate macro-RAFT agent mediated dispersion polymerization of styrene in the alcoholic solvent under different monomer concentration is performed, and the monomer concentration affecting the morphology of the in situ synthesized nanoobjects of the poly(ethylene glycol)-block-polystyrene (PEG-b-PS) diblock copolymer is investigated.…”

Polyglycerol-poly(ε-caprolactone) block copolymer as a new semi-solid polymeric emulsifier to stabilize O/W nanoemulsions

“…Therefore, various amphiphilic polymers have been studied and used as an emulsifier for industrial applications in the fields of food, cosmetics, drug delivery, etc. [13][14][15][16].…”