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Covalent functionalization of alkyne-decorated multiwalled carbon nanotubes (MWNTs) with a well-defined, azide-derivatized, thermoresponsive diblock copolymer, poly(N,N-dimethylacrylamide)-poly(N-isopropylacrylamide) (PDMA-PNI-PAM) was accomplished by the Cu(I)-catalyzed [3 þ 2] Huisgen cycloaddition. It was found that this reaction could simultaneously increase the molecular size and bonding density of grafted polymers when PDMA-PNIPAM micelles were employed in the coupling system. On the other hand, attachment of molecularly dissolved unimers of high-molecular weight onto the nanotube resulted in low-graft density. The block copolymer bearing azide groups at the PDMA end was prepared by reversible addition-fragmentation transfer polymerization, which formed micelles with a diameter of $40 nm at temperatures above its critical micelle temperature. Scanning electron microscopy was utilized to demonstrate that the coupling reaction was successfully carried out between copolymer micelles and alkyne-bearing MWNTs. FTIR spectroscopy was utilized to follow the introduction and consumption of alkyne groups on the MWNTs. Thermogravimetric analysis indicated that the functionalized MWNTs consisted of about 45% polymer. Transmission electron microscopy was utilized to image polymer-functionalized MWNTs, showing relatively uniform polymer coatings present on the surface of nanotubes. V

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(2013) Well-defined poly(N-isopropylacrylamide) with a bifunctional end-group: synthesis, characterization, and thermoresponsive properties, Designed Monomers and Polymers, 16:5, 465-474, DOI: 10.1080/15685551.2012 In this study, well-defined poly(N-isopropylacrylamide) (PNIPAM) with a bisalkyne end-group was synthesized by reversible addition-fragmentation chain transfer polymerization using 2-(2-(ethylthiocarbonothioylthio)-2-methylpropanoyl-oxy)ethyl 3,5-bis(prop-2-ynyloxy) benzoate (EMEB) as the chain transfer agent. The molecular weight and polydispersity index of polymer was determined by gel permeation chromatography (GPC). The linear increase in molecular weight with conversion, unimodal, and almost symmetrical peak in GPC trace together with low polydispersity indicated the controlled polymerization process of NIPAM mediated by EMEB. Subsequently, the Cu(I)-catalyzed [3 + 2] Huisgen cycloaddition between the end-group of polymer and azide derivatives was carried out to produce PNIPAM, in which the bisfunctional end-group was modified with phenyl, octyl, amido, and hydroxyl groups. After completing the click reaction, the structure of the polymer was characterized carefully by Fourier transform infrared spectroscopy (FTIR), 1 H NMR, and Matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS), indicating the complete consumption of alkyne end-groups. In addition, almost no change in molecular weight as well as the polydispersity was observed by comparison with the GPC traces of polymers before and after click reaction. The cloud point temperatures (T cp s) of the resulting PNIPAM derivatives in aqueous solution were investigated in detail by dynamic light scattering. The results showed that the values of T cp were ranged from 22 to 38°C, which depended largely on end-groups as well as the polymer molecular weights.

In this study, well-defined amphiphilic double-brush copolymers (DBCs) with narrow molecular weight distributions were efficiently synthesized by radical polymerization of macromonomers directed by Pickering emulsion template at oil-water interface.Firstly, well-defined poly(methyl methacrylate)-b-poly(N,N-dimethyl acryamide) (PMMA-b-PDMA) diblock macromonomer carrying a pendent methacryloyl (MA) group at the block junction (MA-PMMA-b-PDMA) was synthesized through sequential atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerization, followed by an acrylation functionalization reaction. The MA-PMMA-b-PDMA macromonomer could self-assemble into core-shell micelles with hydrophobic PMMA-based cores, hydrophilic PDMA shells and MA groups at core-shell boundary. The as-formed core-shell micelles were then employed as emulsifiers for the formation of stabilized oil-in-water (o/w) Pickering emulsion, in which the macromonomer micelles were locked at the oil-water interface and presented Janus-like conformation. At last, the conventional radical polymerization reaction was carried out for the MA groups of the macromonomer micelles absorbed at the oil-water interface using azobiisobutyronitrile (AIBN) pre-encapsulated in the Pickering emulsion oil droplets as initiator, leading to well-defined PMA-g-PMMA/PDMA DBCs with narrow molecular weight distributions. The as-formed DBCs showed higher degrees of polymerization of backbones than the DBCs synthesized by micellar polymerization of the macromonomer in pure water, presumably due to the facilitated propagation reaction between the neighboring micelles in the former cases. The macromonomers and DBCs were carefully characterized by various instrumental analytical techniques. displayed the 1 H NMR spectra of BEMP and BMBP. For BEMP, the respective resonances were clearly assigned, which were in good agreement with the early reports 40 . Different with the 1 H NMR spectrum of BEMP, the spectrum of BMBP showed new resonances at 4.15-4.07 and 1.94 ppm. These resonances were assigned to the methylene protons of -C(Br)COOCH 2 group and the methyl protons of -C(Br)CH 3 group, respectively. The 1 H NMR results confirmed that the designed BMBP was successfully synthesized. Scheme 2. Synthesis routes of BEMP, BMBP, PMMA, PMMA-b-PDMA, MA-PMMA-b-PDMA, and PMA-g-PMMA/PDMA. (i) EMP/DCC/DMAP/acetone, room temperature; (ii) 2-bromoisobutyryl bromide/Et 3 N/CH 2 Cl 2 , room temperature; (iii) MMA/CuBr/PMDETA/anisole; (iv) DMA/AIBN/DMF; (v) methacryloyl chloride,Et 3 N/CH 2 Cl 2 ; (vi) AIBN/70 ℃.Fig. 4 (A) Volume-average distribution of the hydrodynamic diameters of macromonomer micelles in water; (B) TEM image of macromonomer micelles without staining; (C,D) TEM images of macromonomer micelles stained by phosphotungstic acid solution. Core crosslinked star-like (CCS) polymer nanoparticles exhibited excellent emulsifying performances, and can allow for the generation of highly stabilized Pickering emulsions at extremely low contents ...

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It is significant to explore multiresponsive Pickering emulsions because of their flexibility in terms of demulsification in comparison with the single stimuliresponsive systems. In this study, we described a tripleresponsive oil-in-water Pickering emulsion that was stabilized by amphiphilic core cross-linked supramolecular polymer particles (CCSPs). For this purpose, β-cyclodextrin-terminated poly(N-isopropylacrylamide) (PNIPAM-β-CD) and azobenzene-capped poly(4-vinylpyridine) (P4VP-azo) were separately synthesized by reversible addition−fragmentation chain transfer polymerization. By virtue of the inclusion interaction between the β-CD host and the azobenzene guest in dimethyl sulfoxide, the amphiphilic supramolecular block copolymer, poly(4-vinylpyridine)-b-poly(N-isopropylacrylamide) (P4VP-b-PNIPAM), was formed. CCSPs were prepared through the combination of the self-assembly of P4VP-b-PNIPAM in the selective solvent, water, and the cross-linking of the P4VP core with 1,4-dibromobutane. Due to thermoresponsiveness of PNIPAM shells and the supramolecular linkages between the cross-linked hydrophobic P4VP core and hydrophilic PNIPAM shells, the as-prepared CCSPs exhibited temperature-, light-, and amantadine hydrochloride guest-triggered morphological transitions. Such triple-responsive morphological transitions gifted CCSPs stabilized oil-in-water Pickering emulsion with flexible demulsification in response to various factors, such as thermo, light, and amantadine hydrochloride or their combinations. Such triple-responsive oil-in-water Pickering emulsion also provided an ideal platform for heterogeneous reactions conducted at the oil−water interface. A large interfacial area and responsive demulsification allowed the reaction to be performed with an efficient and sustainable pattern.