A convenient one‐pot method for the controlled synthesis of polystyrene‐block‐polycaprolactone (PS‐b‐PCL) copolymers by simultaneous reversible addition–fragmentation chain transfer (RAFT) and ring‐opening polymerization (ROP) processes is reported. The strategy involves the use of 2‐(benzylsulfanylthiocarbonylsulfanyl)ethanol (1) for the dual roles of chain transfer agent (CTA) in the RAFT polymerization of styrene and co‐initiator in the ROP of ε‐caprolactone. One‐pot polymerizations using the electrochemically stable ROP catalyst diphenyl phosphate (DPP) yield well‐defined PS‐b‐PCL in a relatively short reaction time (≈4 h; = 9600?43 600 g mol?1; / = 1.21?1.57). Because the hydroxyl group is strategically located on the Z substituent of the CTA, segments of these diblock copolymers are connected through a trithiocarbonate group, thus offering an easy way for subsequent growth of a third segment between PS and PCL. In contrast, an oxidatively unstable Sn(Oct)2 ROP catalyst reacts with (1) leading to multimodal distributions of polymer chains with variable composition.
A new monomer, N‐hexenylacrylamide, is copolymerized with N‐isopropylacrylamide by reversible addition‐fragmentation chain transfer (RAFT) polymerization using a carboxylic‐acid‐functionalized RAFT agent. Subsequently, the resulting functional copolymers are reacted with acetylated thiogalactose via a thiol‐ene reaction. After deprotection of the sugar acetyl groups, the glycopolymers show a lower critical solution temperature (LCST) behavior, as confirmed by turbidity measurements. One of these glycopolymers is subsequently immobilized onto solid supports. The obtained products are characterized by attenuated total reflection Fourier transform IR (ATR FTIR) spectroscopy, thermal gravimmetric analysis (TGA), and elemental analysis, confirming the immobilization of the glycopolymer. Additionally, the glycopolymer‐functionalized support shows interaction with the lectin RCA120.
Stationary and time‐resolved electron spin resonance spectroscopy measurements are employed to investigate the kinetics of the surface‐initiated reversible addition fragmentation chain transfer (RAFT) polymerization of n‐butyl acrylate from silica nanoparticles using both R‐ and Z‐group‐attached trithiocarbonates as RAFT agents. The obtained kinetic parameters reveal that the addition rate coefficient in the main equilibrium of RAFT graft polymerizations is significantly smaller than the one for comparable RAFT polymerizations in solution phase, as translational diffusion of surface‐attached molecules is limited. In comparison to the R‐group approach, the equilibrium constants of the Z‐group approach are about one to two orders of magnitude smaller due to a stronger shielding of the RAFT moieties.
Optical diffraction measurements are reported for in situ observation of swelling and collapsing of responsive hydrogel nanostructures. The optical signal is enhanced by probing the surface carrying periodic arrays of hydrogel nanostructures by resonantly excited optical waveguide modes. UV‐nanoimprint lithography is employed for the preparation of the arrays of nanopillars from photo‐crosslinked N‐isopropylacrylamide (pNIPAAm)‐based hydrogel that are covalently tethered to a gold surface. The thermo‐responsive properties of such pNIPAAm nanopillars that swell in 3D are compared to those of a thin film prepared from the identical material and that is allowed to swell predominantly in 1D. The nanopillars with a diameter of ≈100 nm and aspect ratio of 2 swell by a factor of ≈6 as determined by optical measurements supported by simulations that are compared to morphological characteristics obtained from atomic force microscopy. Bending of nanopillars above the lower critical solution temperature (LCST), erasure of the topographic structure by drying at temperature below the LCST, and recovery by subsequent swelling below the LCST and drying at temperature above the LCST are observed.
A fluorine‐containing difunctional benzoxazine is synthesized by hydrosilylation of a monofunctional benzoxazine based on o‐allylphenol and p‐fluoroaniline. Besides the intramolecular and intermolecular hydrogen bonding associated with the nitrogen and oxygen atoms in the oxazine ring, specific self‐complementary intermolecular Ar F···HO hydrogen bonding is formed in the polymerization of the benzoxazine, which leads to the resultant polybenzoxazine possessing a broad glass transition temperature range and showing two not well‐separated transitions. Based on the two glass transition temperatures, the polybenzoxazine exhibits triple‐shape‐memory behaviors by manipulating temperature and strain in the shape fixing process under tensile and bending modes. The dynamic mechanical and shape‐memory properties of the polybenzoxazine are influenced by the combined effect of the cross‐linking density and the Ar F···HO hydrogen bonding.
Supramolecular hydrogels composed of poly(ethylene glycol) (PEG) containing polymer and α‐cyclodextrins (α‐CDs) show great potential in drug delivery. Herein, PEGylated magnetic nanoparticles (MNPs) and gold nanoparticles (AuNPs) of ≈10 nm are synthesized in the presence of poly(poly(ethylene glycol) methyl ether acrylate) (PPEGMA) grafted poly(acrylic acid) copolymers (PPEGMA‐co‐PAA, P1) and PPEGMA grafted poly(2‐(dimethylamino)ethyl methacrylate) copolymers (PPEGMA‐co‐PDMAEMA, P2), respectively. The produced PEGylated NPs are hybridized into supramolecular hydrogels by mixing them with α‐CDs through inclusion complexation between PEG branches and α‐CDs. As a result, supramolecular hydrogels hybridized with inorganic MNPs and AuNPs are prepared and characterized by rheological measurements, X‐ray diffraction, and scanning electron microscopy. Both MNP and AuNP hybrid hydrogels show reversible sol–gel transition, which is stimulated by changes in temperature and pH. The nanoparticles hybridized in the hydrogels can be released gradually in the process of hydrogel disruption. These hydrogels may have potential applications in biomaterials and drug delivery.
This investigation reports preparation of polyfluoroacrylate/clay nanocomposite with armored and encapsulated morphology via in situ reversible addition–fragmentation chain transfer (RAFT) polymerization in miniemulsion. In this case, 2,2,3,3,4,4,4‐heptafluoro butyl acrylate (HFBA) is polymerized in miniemulsion in the presence of sodium montmorillonite (NaMMT) using 2‐cyanopropyl dodecyl trithiocarbonate (CPDTC) as a RAFT agent. Gel permeation chromatography (GPC) analysis shows that the polymers have controlled molecular weights as well as narrow dispersity (? ≈ 1.1). The morphology of nanoclay can be tuned by varying the interaction with different functional comonomers. Nanoclay is encapsulated and intercalated in presence of poly (ethylene glycol) methyl ether methacrylate (PEGMEMA) as comonomer. Addition of 2‐acryloxy ethyl trimethyl ammonium chloride (AETAC) as functional comonomer leads to exfoliation of nanoclay resulting armored morphology, as evidenced by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) analyses. Poly(2,2,3,3,4,4,4‐heptafluoro butyl acrylate) (PHFBA) armored with nanoclay shows improved thermal stability and water resistance.
The controlled radical polymerization of 2‐vinylpyridine is reported using commercial blue light‐emitting diodes as visible light source in the presence of S‐1‐dodecyl‐S′‐(α,α′‐dimethyl‐α″‐aceticacid) trithiocarbonate without exogenous initiators or photocatalysts. With this system, poly(2‐vinylpyridine) with well‐regulated molecular weight and narrow dispersity (?) (? = 1.13) and a conversion efficiency of 84.9% is obtained after 9 h irradiation. The polymerization can be instantly switch “on” or “off” in response to visible light while maintaining a linear increase in molecular weight with conversion and first order kinetics. These results demonstrate the simplicity and efficiency of the photocatalysts‐free, visible light mediated reversible addition fragmentation chain transfer polymerization as a platform to achieve well‐defined poly(2‐vinylpyridine) under mild conditions.
Reverse iodine transfer polymerization (RITP) of 1,1,2,2‐tetrahydroperfluorodecyl acrylate (FDA) is successfully performed in supercritical carbon dioxide (scCO2) at 70 °C under a CO2 pressure of 300 bar. PolyFDA (PFDA) of increasing molecular weights (from 10 000 to 100 000 g mol?1) is synthesized with good agreement between theoretical, 1H NMR spectroscopy and and size exclusion chromatography/refractive index/right‐angle laser‐light scattering/differential viscometer (SEC/RI/RALLS/DV)‐estimated molecular weights (). Furthermore, the increase of goes with a decrease of the dispersity of the polymers (? from 2.06 to 1.33), which is consistent with a controlled radical polymerization (CRP). Lastly, the structure of final PFDA and therefore the RITP process are confirmed by matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) analyses.
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.
Alternating copolymers of an oligopeptide (N3‐GVGV‐N3, where G: glycine; V: valine) and an oligothiophene (5,5′‐bis(ethynyl)‐3,3'‐dioctyltetrathiophene) are prepared by click chemistry. The experimental results discover that these copolymers exhibit strong molecular‐weight‐dependent self‐assembly behaviors. The copolymer P1 with the lowest weight‐average molecular weight ( = 7400 g mol?1), assembles into well‐ordered fibrous nanostructures. P3 ( = 16 980 g mol?1) assembles into nanoballs. P2, which has the medium between P1 and P3, ( = 14 800 g mol?1), exhibits more‐complicated self‐assembly behaviors, more like a transition state between the other two. All of the results suggest the self‐assembly ability of these oligopeptide segments might be the major reason for the nano‐structure evolution.
In this work, an agarose/poly(acrylamide‐co‐acrylic acid) interpenetrating network hydrogel is prepared by the photopolymerization of acrylamide, acrylic acid, and N ,N ′‐methylenebisacrylamide within agarose network at its gel state. The as‐prepared hydrogel exhibits two independent kinds of shape memory effects. The thermal‐activated shape memory behavior is attributed to the reversible coil‐helix transformation of agarose, within the permanently cross‐linked poly(acrylamide‐co‐acrylic acid) network; the light triggered shape recovery is driven by the dissociation of the complexes between carboxyl groups and Fe(III) ions, due to the photoreduction of Fe(III) to Fe(II) in the presence of citric acid. The versatile and simple strategy as presented here should be beneficial for the design of dual‐activated shape memory hydrogels and foster their use in a number of fields such as biomaterials, soft robotics, smart actuators, and sensors.
Thermoresponsive polypeptoids are promising candidates for medical applications due to their biomimetic properties. When such polymers are grafted on magnetic nanoparticles, materials can be obtained that combine a temperature‐triggered solubility transition with magnetic extraction. The synthesis of monodisperse, superparamagnetic iron oxide nanoparticles is described with densely surface‐grafted polypeptoid shells that have tunable thermoresponsive colloidal stability. The synthesis combines ligand exchange with controlled surface‐initiated polymerization of N‐substituted N‐carboxyanhydrides for the preparation of well‐defined core–shell nanoparticles.
A series of acrylate‐based shape‐memory materials are synthesized from bisphenol A diacrylate monomers as crosslinking agents. Networks are synthesized by keeping constant the content of bisphenol A‐based crosslinking agent and systematically varying the content ratio of different monofunctional chain builder monomers. The implications of the structure of bisphenol A‐based monomers and the chemical structure and content of monofunctional monomers on thermomechanical properties are discussed. Thermomechanical properties are analyzed using dynamic mechanical analyses and mechanical properties are studied at room temperature and at the onset of the glass transition temperature. Shape‐memory performances under isothermal and transient temperature conditions are also carried out. Tensile tests show excellent values of stress at break up to 45 and 15 MPa at room and high temperature, respectively. The measurements show excellent shape recovery and shape fixity ratios, ≈95% and 97%, respectively. These materials also show very high recovery velocities under transient temperature conditions, up to 24% min?1, and very short recovery times, up to 1.5 s, under isothermal conditions in a water bath. The results confirm that networks synthesized from bisphenol A crosslinkers are promising shape‐memory materials.
Cu(I)‐catalyzed azide–alkyne cycloaddition is shown here to be an efficient method to create adhesive materials in situ between glass and copper surfaces. Twelve formulations show adhesive strengths greater than a commercial product under comparable conditions, with the best combination of monomers the same as that previously developed for copper–copper adhesion. Strong adhesion is also achieved under water, an environment in which the commercial glue fails. Brass, iron, and stainless steel could also be adhered to glass using different formulations, but aluminum could not. The concentration and molar ratio of monomers, curing temperature, prefunctionalization of the glass surface, and the incorporation of flexibility‐inducing components all have significant effects on adhesive performance.
Anionic polymerization of n‐butyl acrylate (nBA) in toluene initiated with a binary initiator, isopropyl α‐lithioisobutyrate/ethylaluminum bis(2,6‐di‐tert‐butylphenoxide) at ?60 °C, is terminated with ethyl α‐(chloromethyl)acrylate (ECMA) to afford a poly(nBA) possessing an acryloyl group at the terminal with 80% of termination efficiency. The reactivity of nBA against a polymer anion of methyl methacrylate formed under identical conditions is estimated relative to the termination with ECMA by reacting a mixture of nBA and ECMA followed by 1H NMR spectroscopic chain‐end analysis; the relative reactivity of nBA is found 80 times or more higher than ECMA.
In this paper, the acid–base bifunctional microporous organic nanotube networks (MONNs–SO3H–NH2) are successfully prepared by combination of hyper‐crosslinking core–shell bottlebrush copolymers and a postfunctionalization strategy. Based on the large surface area, good multiporosity interconnectivity, and robust organic frameworks, the acid–base bifunctional MONNs catalyst shows a high catalytic activity and excellent reusability for one‐pot cascade reactions.
In this work, a novel synthesis approach of gold nanohybrid materials (Au/SH‐OPPs) is demonstrated using the thiol‐functionalized organic porous polymers (SH‐OPPs) as a support by a combination of hyper‐cross‐linking and molecular templating of functionalized bottlebrush copolymers. HAuCl4 as the gold source is in situ reduced to produce Au nanoparticles based on the strong action of gold with the thiol groups. The monodispersed Au nanoparticles are anchored on the SH‐OPPs with the small average particle size (3.0 ± 1.0 nm) and the high loading about 18%. Moreover, the resultant Au/SH‐OPPs exhibit excellent catalytic performance for the selective oxidation of benzyl alcohol.
In this study, an effective way is presented to synthesize a mussel‐inspired adhesive from two inexpensive commercially available materials: polyvinyl alcohol (PVA) and 3,4‐dihydroxybenzoic acid via the esterification reaction and deprotection technology. This bioinspired adhesive exhibits good bonding ability on metal, glass, plastic, and wood, and the maximum bonding strength can be up to 4.0 MPa at dry conditions on glass substrate. Meanwhile, this adhesive can also be used as a wet/underwater adhesive. Such a PVA‐based bioinspired adhesive may be used as a potential candidate for applications in industrial field.
The self‐assembly and structure formation in binary blends of asymmetric polystyrene‐block‐poly(4‐vinylpyridine) diblock copolymers in different solvent systems and the bulk morphology of the blend films are studied by using dynamic light scattering, small‐angle X‐ray scattering, and transmission electron microscopy. In dilute solutions, the chains of pure diblock copolymers or binary blends of diblock copolymers having similar or different molecular weights remain as unimers, form common micelles in selective solvents or form unimers in coexistence with micelles in slightly selective solvents or solvent mixtures. The blends show mixing of the chemically similar blocks in the blend films and solutions at high concentrations. A single‐phase with common spherical morphology is formed in the blend films similar with the morphology of the individual components in the pure state. The characteristic length scale of the blends depends on the number average molecular weight following the typical scaling behavior of a strongly segregated block copolymer.
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