Well‐defined PEO‐b‐PMMA was prepared, initiated by macroinitiator PEO‐Br, by means of ATRP, where esterification of the terminal hydroxyl group of PEO with 2‐bromoisobutyryl bromide yielded a macroinitiator PEO‐Br. Highly ordered microporous films (hexagonal pattern) were constructed by emulsion micelles of such amphiphilic diblock copolymer formed from a solution with CHCl3/H2O/THF = 100:5:10 (v/v). We also constructed the microporous films using diblock copolymer by the current water‐assisted method.
ATRP of 2‐(N,N‐dimethylamino)ethyl acrylate (DMAEA) was investigated using CuBr or CuCl with different multidentate ligands. The catalyst was found active for DMAEA polymerization when ligated with tris[2‐(N,N‐dimethylamino)ethyl]amine. Good control over molecular weight was achieved, but quaternization of the terminal monomeric/polymeric tertiary amine by the C Br group of polyDMAEA caused chain termination. Using a chloride‐based system helped to suppress chain termination. Amphiphilic poly(methyl acrylate)‐block‐polyDMAEA was synthesized using polyMA as a macroinitiator.
Molecular weights and polydispersities of polyDMAEA versus DMAEA conversion for different catalyst systems. 相似文献
A novel well‐defined amphiphilic block copolymer, with the polyhedral oligomeric silsesquioxane (POSS) moiety at the junction of the two blocks of polystyrene and poly(ethylene oxide) (PEO), was designed and synthesized. First, a macroinitiator containing a POSS moiety and a PEO chain was prepared and then atom transfer radical polymerization of styrene was carried out in the presence of the macroinitiator in bulk. The polymerization results show that the process bears the characteristics of controlled/living free radical polymerizations. The structure and molecular weight of the polymers were characterized by GPC, 1H NMR, and FT‐IR spectroscopy. The self‐assembly behaviors of the polymers was investigated by TEM and SEM. It was observed that the polymers can self‐assemble into vesicles in aqueous solution.
Summary: A novel ABC triblock copolymer with a rigid‐rod block was synthesized by atom transfer radical polymerization (ATRP). First, a poly(ethylene oxide) (PEO)‐Br macroinitiator was synthesized by esterification of PEO with 2‐bromoisobutyryl bromide, which was subsequently used in the preparation of a poly(ethylene oxide)‐block‐poly(methyl methacrylate) (PEO‐b‐PMMA) diblock copolymer by ATRP. A poly(ethylene oxide)‐block‐poly(methyl methacrylate)‐block‐poly{2,5‐bis[(4‐methoxyphenyl)oxycarbonyl]styrene} (PEO‐b‐PMMA‐b‐PMPCS) triblock copolymer was then synthesized by ATRP using PEO‐b‐PMMA as a macroinitiator.
ABC triblock copolymer with a rigid‐rod block. 相似文献
The synthesis of diblock copolymers of aromatic polyether and polyacrylonitrile (PAN) was conducted by chain‐growth condensation polymerization (CGCP) and atom transfer radical polymerization (ATRP) from an orthogonal initiator. When CGCP for aromatic polyether was carried out from a PAN macroinitiator obtained by ATRP with an orthogonal initiator, decomposition of the PAN backbone occurred. However, when ATRP of acrylonitrile was conducted from an aromatic polyether macroinitiator obtained by CGCP followed by introduction of an ATRP initiator unit, the polymerization proceeded in a well‐controlled manner to yield aromatic polyether‐block‐polyacrylonitrile (polyether‐b‐PAN) with low polydispersity. This block copolymer self‐assembled in N,N‐dimethylformamide to form bundle‐like or spherical aggregates, depending on the length of the PAN units in the block copolymer.
A novel chlorotitanium calix[4]arene complex was synthesized and tested, without activator, as catalyst for the polymerization of L ‐ and rac‐lactide under solvent‐free conditions. The catalyst displayed high activity, which depended on the monomer‐to‐catalyst molar ratio, and led to highly isotactic PLLA. Despite concomitant transesterification during the polymerization, polylactide formation was well‐controlled, the molar mass distribution indexes remaining in the restricted range of 1.2–1.4.
Self‐stabilized nanoparticles with a temperature‐responsive poly[(N,N‐diethylacrylamide)‐co‐(N,N′‐methylenebisacrylamide)] microgel core and a covalently attached hairy shell were synthesized via a simple nitroxide‐mediated controlled free‐radical aqueous dispersion polymerization, using a poly(sodium acrylate) alkoxyamine macroinitiator. With this method, high solid content, surfactant‐free particle suspensions were prepared, with diameter ranging from 49 to 118 nm at high temperature, and able to reversibly swell with water at low temperature. The proposed method requires a limited number of reagents in a simple polymerization procedure and thus avoids many drawbacks generally encountered in the synthesis of thermally responsive microgel particles.
Summary: An enzymatic one‐pot procedure has been developed for the synthesis of difunctional polyesters containing terminal thiols and acrylates. Candida antarctica lipase B was used as a catalyst for the ring‐opening polymerization of ω‐pentadecalactone. The polymerization was initiated with 6‐mercaptohexanol, then terminated with γ‐thiobutyrolactone or vinyl acrylate to create two types of difunctional polyesters with a very high content of thiol‐thiol or thiol‐acrylate end‐groups.
A novel α,ω‐heterofunctional poly(ethylene oxide) (PEO) macromonomer possessing methacryloyl and thienyl end groups was prepared by ring‐opening polymerization of ethylene oxide initiated by potassium thienylethoxide and termination of the living PEO ends with methacryloyl chloride. Incorporation of methacryloyl and thienyl groups was confirmed by free‐radical and oxidative polymerization processes, respectively, and by means of 1H NMR analysis.
Well‐defined diblock condensation copolymers composed of an aromatic polyamide and an aromatic polyether have been synthesized by means of successive chain‐growth condensation polymerizations. Polymerization of a polyamide monomer with an orthogonally difunctional initiator is accompanied with side reactions. On the other hand, polymerization with a monofunctional initiator afforded well‐defined polyamide, which has been converted into a macroinitiator by introduction of a terminal 4‐fluorobenzophenone unit. Well‐defined diblock copolymers are obtained by polymerization of a polyether monomer in the presence of this macroinitiator.
Summary: Thiol‐reactive‐functionality decorated multi‐walled carbon nanotubes (MWNTs) have been obtained. Trithiocarbonate‐ended poly(N‐(2‐hydroxypropyl)methacrylamide) (PHPMA) is prepared by reversible addition‐fragmentation chain transfer (RAFT) polymerization of N‐(2‐hydroxypropyl)methacrylamide (HPMA) using S‐1‐dodecyl‐S′‐(α,α′‐dimethyl‐α″‐acetic acid)trithiocarbonate as chain transfer agent, subsequently, thiol‐terminated PHPMA (PHPMA‐SH) is obtained by treating trithiocarbonate‐ended PHPMA with hexylamine. The PHPMA‐S‐S‐MWNT conjugate is formed by simply stirring the mixture of thiol‐reactive‐functionality decorated MWNTs with PHPMA‐SH in phosphate buffered saline by a thiol‐coupling reaction. FT‐IR, HRTEM, 1H NMR, and TGA results show that this thiol‐coupling reaction is effective to produce aqueous soluble polymer–MWNT conjugates under mild conditions.
Thiol‐reactive‐functionality decorated multi‐walled carbon nanotubes are modified with thiol end‐capped polymers by a thiol‐coupling reaction. 相似文献
A novel method is described for transforming an anionic polymerization process into a cationic polymerization process assisted by organosilyl groups. The reaction of the p‐tolyldimethylsilyl end group of polystyrene and trifluoromethanesulfonic acid produced a silyl triflate end group that served as a macroinitiator for the living cationic polymerization of isobutyl vinyl ether. The Si O linkage in the block copolymers underwent specific cleavage by reaction with tetrabutylammonium fluoride.
Synthesis of a water‐soluble polydiacetylene has been achieved by topochemical polymerization in the solid state of the bis(N‐methylimidazolium)diacetylene monomer. Structural characterization for the monomer by X‐ray diffraction and NMR spectroscopy supports a photopolymerization initiated at the surface. Characterization of the polymer (NMR, UV and Raman spectroscopy, and dynamic light scattering) is given along with a molecular modelling interpretation of the polymerization in the solid state.
We applied 1,3‐dipolar cycloaddition to bind ethynylferrocene onto 6I‐azido‐6I‐deoxycyclomaltoheptaose under microwave assisted conditions. The process was investigated by 1H NMR, FT‐IR spectroscopy, and MALDI‐TOF mass spectrometry. The ability of the synthesized compound to self‐organize to cyclic supramolecular structures was investigated by dynamic light scattering measurements and cryo‐transmission electron microscopy.
The thermal ring‐opening polymerization of 5‐benzyloxy‐trimethylene carbonate (BTMC) in bulk in the absence of any catalyst resulted in high molecular weight poly(BTMC) ( = 80 300) and subsequent catalytic hydrogenolysis resulted in functional poly(5‐hydroxyl‐trimethylene carbonate) (PHTMC). Similar spontaneous polymerization of BTMC in the presence of PEG ( = 2 000) as a macroinitiator can provide amphiphilic block polymers. The results revealed that the thermal non‐catalyst (co)polymerization of BTMC is a highly attractive preparative method because of the lack of usage of toxic initiators or catalysts. Furthermore, an evaluation of the degradation and cytotoxicity of PHTMC demonstrated enhanced degradability compared to poly(trimethylene carbonate) and similar toxicity compared to PLGA, showing PHTMC to be a promising biomaterial.
While miniemulsion polymerization has proven to be well‐suited for conducting living/controlled radical polymerizations, emulsion polymerizations have proven to be far more challenging. Ab initio emulsion polymerizations, in which monomer droplets are present during polymerization, have thus far not been successful with TEMPO‐mediated polymerizations, as a result of colloidal instability and coagulum formation. By selectively inhibiting polymerization in the monomer droplets, it is demonstrated that droplet polymerization is responsible for the formation of large (>1 µm) particles that can lead to coagulum formation. Furthermore, we show that coagulum‐free latexes can be produced using a TEMPO‐mediated ab initio emulsion polymerization by suppressing droplet polymerization.
A novel synthetic method combining chemo and enzymatic synthesis strategies was employed to prepare a vinyl acetate type monomer, 6‐(4‐methoxybiphenyl‐4′‐oxy)hexyl vinyl hexanedioate (VA‐LC). Homo‐ and copolymers of VA‐LC with maleic anhydride (MAn) were prepared by conventional free radical polymerization using 2,2′‐azobisisobutyronitrile (AIBN) and 1,1′‐azobis (cyclohexane carbonitrile) (AHCN) as an initiator at 95 and 60 °C, respectively. The thermal properties of the generated polymeric material were investigated by differential scanning calorimetry (DSC), and the optical texture was inspected by polarizing optical microscopy (POM). While the monomer VA‐LC does not exhibit liquid‐crystalline properties, poly(VA‐LC), and the alternating copolymer of VA‐LC with maleic anhydride both displayed such properties.
The influence of the initial macroinitiator concentration ([PT]0) on compartmentalization effects (segregation effects and confined space effects) in 2,2,6,6‐tetramethylpiperidinyl‐1‐oxy (TEMPO)‐mediated radical polymerization of styrene in a dispersed system at 125 °C has been investigated by simulations employing modified Smith‐Ewart equations. The modeling approach accounts for compartmentalization of both propagating radicals and nitroxide, as well as the generation of radicals by thermal initiation of styrene. The manifestation of compartmentalization effects occurs at significantly greater particle diameters (d) for low [PT]0; at [PT]0 = 0.002 M , the polymerization rate, control and livingness are affected by compartmentalization for d < 120 nm, whereas the system behaves as in the corresponding bulk system for d > 45 nm at [PT]0 = 0.2 M . The results are discussed with regards to the specific effects of compartmentalization on deactivation and bimolecular termination.
Summary: Poly(vinyl acetate) macroinitiators end‐capped by a Co(acac)2 complex (PVAc–Co(acac)2), prepared in bulk by cobalt‐mediated radical polymerization (CMRP), are used for the controlled radical polymerization of vinyl acetate in miniemulsion to give high‐molecular‐weight polymers and high monomer conversion. Stable poly(vinyl acetate) latexes with solid contents ranging from 25 to 30 wt.‐% are prepared within unusually short reaction times (∼1 h) at low temperatures (0–30 °C).
SEC chromatograms for the PVAc–Co(acac)2 macroinitiator and PVAc latex obtained under ultrasonication for 6 min at 0 °C (79% monomer conversion). 相似文献
