Novel SiO2‐supported silyl‐chromate(Cr)/imido‐vanadium(V) (Cr‐imidoV) bimetallic catalysts for ethylene and ethylene/α‐olefin polymerization are investigated. These catalysts are prepared using the residual surface hydroxyl groups in SiO2‐supported imido‐vanadium catalysts to further support bis(triphenylsilyl) chromate (BC) in order to get the merits from both the SiO2‐supported imido vanadium catalyst and the SiO2‐supported silyl chromate S‐2 catalyst. By investigation of the polymerization behavior and the microstructures of their polymers, several vital factors such as the addition amount of imido vanadium active centers and the dosage of 1‐hexene in the ethylene homopolymerization and ethylene/1‐hexene copolymerization are systematically investigated. Compared with the traditional S‐2 catalyst and our previously reported SiO2‐supported silyl‐chromate(Cr)/vanadium(V)‐oxide (Cr‐V) bimetallic catalyst, the novel Cr‐imidoV bimetallic catalysts show even higher activity and better 1‐hexene incorporation ability, together with higher molecular weight (MW) and bimodal molecular‐weight distribution (MWD).
Desorption of thiol‐based self‐assembled monolayers on gold surfaces makes surface‐initiated atom transfer radical polymerization (SI‐ATRP) challenging and results in reduced density “grafted from” polymer film. In this work, in situ attenuated total reflectance‐Fourier transform infrared (ATR‐FTIR) spectroscopy shows that copper‐based catalysts typically used in SI‐ATRP cause substantial desorption of bound thiol‐based initiator films from gold surfaces. Other reaction conditions factors such as low temperature, presence of radicals, and solvents selection have relatively minor effects in comparison. Indeed, the desorption of initiator films is reduced from more than 80% to about 45% when CuCl catalyst is used for the ATRP of styrene instead of CuBr catalyst. However, the polymerization rate is significantly slower in this case.
A novel Janus compound containing azo‐based thermal initiator and bromo‐based atom transfer radical polymerization (ATRP) initiator group is synthesized. Such compound can be applied in the living radical polymerization of alkyl methacrylate monomers, such as methyl methacrylate, tert‐butyl methacrylate, and 2‐(N,N‐dimethylamino) ethyl methacrylate. Polymers with controlled molecular weights and narrow molecular weight distributions are obtained. The structure of polymers is identified by 1H NMR spectroscopy and matrix‐assisted laser desorption ionization time‐of‐flight mass spectrum. A modified initiator for continuous activator regeneration ATRP mechanism is proposed according to the polymerization behavior, hydrolysis of chain backbone, and end group identification.
Commercially available hydrophobic porphyrins are investigated as an environmentally friendly catalytic system for iron‐mediated atom transfer radical polymerization (ATRP) of poly(ethylene glycol) monomethyl ether methacrylate (PEGMA). Polymerizations in organic solvent are optimized using activators generated by electron transfer (AGET ATRP), based on iron(III)–porphyrin complexes, and tin(II) 2‐ethyl hexanoate or ascorbic acid as a reducing agent. Copper‐free PPEGMA macromolecules are obtained with high conversion, controlled molecular weight, and polydispersity index compared with standard copper‐based ATRP. The facile preparation and availability of the catalyst, together with its expected low toxicity, represent clear advantages for the synthesis of PPEGMA‐based materials for biomedical use.
The homo‐ and copolymerizations of 1,3‐butadiene and isoprene are examined by using neodymium isopropoxide [Nd(Oi‐Pr)3] as a catalyst, in combination with a methylaluminoxane (MAO) cocatalyst. In the homopolymerization of 1,3‐butadiene, the binary Nd(Oi‐Pr)3/MAO catalyst works quite effectively, to afford polymers with high molecular weight ( ≈ 105 g mol‐1), narrow molecular‐weight distribution (MWD) (/ = 1.4–1.6), and cis‐1,4‐rich structure (87–96%). Ternary catalysts that further contain chlorine sources enhance both catalytic activity and cis‐1,4 selectivity. In the copolymerization of 1,3‐butadiene and isoprene, the copolymers feature high , unimodal gel‐permeation chromatography (GPC) profiles, and narrow MWD. Most importantly, the ternary Nd(Oi‐Pr)3/MAO/t‐BuCl catalyst affords a copolymer with high cis‐1,4 content in both monomer units (>95%).
The controlled radical polymerization (RAFT polymerization) of semiconducting polymers based on poly(4,4′‐dimethyl‐triphenylamine) is described. These polymers are afterward end‐functionalized with a photocleavable group and an anchor unit (catechol) for oxidic nanoparticles (NPs). Serving as a reference, polystyrene oligomers with the same end groups are also synthesized. Using these polymers allows functionalization of the TiO2‐NPs, leading to an improved solubility and miscibility in organic solvents or polymer matrices. Irradiation in the UV region is used to split the photocleavable group and remove the polymer chains from the NPs, which leads to their aggregation.
A facile surface modification procedure for electrospun poly(butylene terephthalate) (PBT) fibers by surface‐initiated atom transfer radical polymerization (SI‐ATRP) is reported. Initiators are introduced through aminolysis and chemical vapor adsorption. SI‐ATRP is subsequently carried out to prepare a polymer‐grafted layer at the PBT fiber surface without altering the fiber geometry. After modification with a zwitterionic poly(sulfobetaine), poly(3‐(N‐2‐methacryloyloxyethyl‐N,N‐dimethyl) ammonatopropanesulfonate), the surface is superhydrophilic. The surface properties are thermally stable due to the high melting temperature of the PBT crystallites and are maintained for a prolonged period.
Three ionic monomers based on a 1‐vinylimidazolium cation, 1‐vinyl‐3‐methylimidazolium methyl sulfate, 1‐vinyl‐3‐ethylimidazolium ethyl sulfate, and 1‐vinyl‐3‐propylimidazolium propyl sulfate are synthesized and characterized by thermal and spectroscopic methods. The ionic‐liquid monomers (ILMs) are prepared using a halide‐free route under ambient conditions by the quaternization reaction of 1‐vinylimidazoles with alkyl sulfates. Through free‐radical polymerization and rheology analysis, solid freestanding linear polymeric‐ionic‐liquid (PILs) films are obtained with a tanδ value as low as 0.180. After polymerization, thermal methods show the linear PILs to possess a thermal stability of up to 340 °C, while rheology analysis reveals the films to have a storage moduli value as high as 4.64 × 106 Pa.
A novel strategy, based on surface‐initiated grafting polymerization and post‐polymerization thiol‐yne click chemistry, with Ir(ppy)3 as a sole photoredox catalyst, under visible light irradiation is developed. The “livingness” of the grafting polymerization is demonstrated by the linear increase of the graft yield with irradiation time and the block grafting polymerization. Then, acetenyl groups of poly(propargyl methacrylate) (PPMA) grafting chains are reacted with pentaerythritoltetra‐(3‐mercaptopropionate) via the thiol‐yne click reaction. The successful introduction of reactive thiol groups onto the low‐density polyethylene‐graft‐poly(propargyl methacrylate) (LDPE‐g‐PPMA) films is demonstrated by Fourier transform IR (FTIR) and X‐ray photoelectron spectra (XPS) spectroscopy, and the thiol‐ene click reaction with N‐(1‐pyrenyl) maleimide.
Facile synthesis of a silicon surface modified by poly(N‐isopropylacrylamide‐co‐N‐acryloyl glucosamine) [poly(NIPAAm‐co‐AGA)] brushes prepared by surface‐initiated single electron transfer‐living radical polymerization (SET‐LRP) in water is described. The copolymerization exhibits a fast polymerization rate and good controllability. Moreover, copolymers with variable AGA content and comparable thickness are synthesized and the effect of the AGA content on the wettability and thermoresponsive property of the surface are studied. Also, both the non‐specific protein resistance ability and the specific protein adsorption ability of the Si‐poly(NIPAAm‐co‐AGA) surface are investigated and the results indicate that the copolymer‐grafted surface demonstrates enhanced resistance to non‐specific protein adsorption and shows selective recognition of Concanavalin A (Con A). Together, these results prove that aqueous SET‐LRP is promising for facile surface modification.
Supramolecular antioxidant complexes are prepared by the non‐covalent assembly of succinic acid‐modified hyperbranched polyglycerols (PGSAs) and tyramine antioxidant compounds. Using this approach, various supramolecular dendritic polymers based on carboxylic acid‐modified hyperbranched polyglycerol with different molecular weights and different numbers of antioxidant phenols are prepared and characterized by FTIR and NMR spectroscopy as well as via dynamic light scattering (DLS). The local phenolic concentration in this supramolecular architecture plays a key role for their enhanced antioxidant capacity, as shown by oxygen radical absorbance capacity assay (ORAC).
A newly established catalyst system for oxygen‐oxidative polymerization of diphenyl disulfide is reported. Combination of vanadyl compounds (e.g., VO(acac)2) and triphenylmethylium tetrakis(pentafluorophenyl)borate (TrB(C6F5)4) proceeds the polymerization to give poly(1,4‐phenylene sulfide) (PPS) at 100 °C. When triphenylmethylium tetrafluoroborate (TrBF4) is applied with vanadyl tetraphenylporphyrin (VO(TPP)) or N,N′‐(ethylenebis(salicylideneaminato))oxovanadium (VO(salen)), PPS is also given via polymerization under conditions near 160 °C. Combination of the vanadyl complex and the borate affords the first protic‐acid‐free catalytic system for the polymerization of the disulfide, suggesting the overall reaction to produce PPS and H2O from O2 and protons that are eliminated from the monomer.
Poly(methyl methacrylate)‐block‐poly(4‐vinylpyridine), polystyrene‐block‐poly(4‐vinyl pyridine), and poly(ethylene glycol)‐block‐poly(4‐vinylpyridine) block copolymers are synthesized by successive atom transfer radical polymerization (ATRP), single‐electron‐transfer nitroxide‐radical‐coupling (SET‐NRC) and nitroxide‐mediated polymerization (NMP). This paper demonstrates that this new approach offers an efficient method for the preparation of 4‐vinylpyridine‐containing copolymers.
Photoinduced Cu(0)‐mediated atom transfer radical polymerization (ATRP) of methyl methacrylate is investigated by using Cu(0)/N,N,N′,N″,N″‐pentamethyldiethylenetriamine as the catalyst, ethyl 2‐bromopropionate as the initiator, and dimethyl sulfoxide as the solvent. The effect of light on the conventional Cu(0)‐mediated ATRP and molecular weight characteristics of the obtained polymers are described. Although the polymerization can be achieved in the absence of light, low initiation efficiency of the process is observed. By introducing UV light and additional Cu(II) deactivator, not only the rate of polymerization is increased, but also well‐controlled polymers with narrow‐molecular‐weight distributions at ambient conditions are obtained. The chain extension study clearly confirms high end‐group fidelity of the polymer that is active in the further polymerization process.
Nonionic aliphatic polymers containing ester and sulfonyl moieties, [poly(ester‐sulfones)s] were found to undergo anode‐selective electrophoresis under electrophoretic deposition conditions. Herein are reported the syntheses of unsaturated nonionic polyesters containing sulfide linkages and double bonds on the polymer backbone via acyclic diene metathesis polymerization using a Grubbs' catalyst. Subsequent oxone oxidation was carried out, affording the corresponding poly(ester‐sulfone), followed by electrophoretic deposition of the unsaturated poly(ester‐sulfone) onto stainless steel. Subsequent UV‐irradiation cured the deposited film, improving the peeling strength of the coating.
The Passerini three‐component reaction is applied to synthesize, in a one‐step procedure, diverse asymmetric α,ω‐dienes containing an acrylate and a terminal olefin. Such monomers are well known to undergo head‐to‐tail acyclic diene metathesis (ADMET) polymerization due to the high cross‐metathesis selectivity between acrylates and terminal olefins. Additionally, amphiphilic block copolymers are synthesized using a monofunctional PEG480 monoacrylate, which acts as a selective chain‐transfer agent during the polymerization process. Thus, control over the molecular weight of the amphiphilic ADMET polymers is shown by using different ratios of monomer and chain‐transfer agent. All the polymers are thoroughly characterized, and their ability to form nanoparticles in aqueous solution is studied.
An amphiphilic penta‐telechelic polyhedral oligomeric silsesquioxane (POSS)‐containing inorganic/organic hybrid poly(acrylic acid), (Glu‐PAA‐POSS5), is prepared by hydrolysis of penta‐telechelic poly(tert‐butyl acrylate) (Glu‐PtBA‐POSS5), synthesized by the combination of atom transfer radical polymerization (ATRP) and a “click” reaction. The self‐assembly behavior of Glu‐PAA‐POSS5 in aqueous solution at pH 8.5 is investigated by using transmission electron microscopy (TEM), scanning electronic microscopy (SEM), atomic force microscopy (AFM), and dynamic light scattering (DLS). The results show that Glu‐PAA‐POSS5, with a long poly(acrylic acid) (PAA) chain, can self‐assemble in water into giant capsules, which provides an optional approach in the construction of capsules.
A novel symmetrical selenium‐based reversible addition‐fragmentation chain transfer (RAFT) agent, Se,Se’‐dibenzyl carbonodiselenothioate (Se‐RAFT), is synthesized and used in the RAFT polymerization of styrene. The results obtained show that the Se‐RAFT agent is involved in the polymerization of styrene, as evidenced by narrow molar‐mass distributions (/ < 1.6) and the incorporation of the Se‐RAFT moiety into the resultant polymer. The latter is confirmed by aminolysis, NMR spectroscopy, size‐exclusion chromatography (SEC) and UV spectroscopy. This work provides detailed insight into the Se‐RAFT polymerization mechanism. The Se‐RAFT agent is unique in that the stabilizing and leaving groups are identical.
The presence of different commonly used induced condensing agents (ICAs) in the gas phase polymerization of ethylene on the supported catalyst has a significant impact on the crystallinity and the molecular weight distribution of the resulting high density polyethylene. The crystallinity of the polymer is found to be higher in the presence of vaporized n‐pentane or n‐hexane, than in “dry mode” (i.e., with no ICA). This is primarily attributed to the mechanism of crystallization of polymer chains in presence of the solubilized ICA which might act to promote solvent vapor annealing. In addition, vaporized ICA also provokes a significant increase in the weight average molecular weight, with values being estimated at over one million.
The synthesis of polymers with various functional groups has always been the core of polymer chemistry. Traditionally, there are two approaches to prepare such polymers: i) preparing functional monomers first and then conducting polymerization to get target functional polymers; and ii) post‐modification of a precursor polymer. Both methods unavoidably involve separation and purification of intermediate products, which is laborious and time‐consuming. A one‐pot synthesis strategy, which combines monomer preparation and controlled polymerization in just one reactor to generate well‐defined polymers efficiently, is thus proposed. Recent advances in the one‐pot synthesis of multifunctional polymers through a multicomponent system are provided in this article.
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