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.
Synthesis of complex macromolecular architectures exhibiting no chain ends such as flower‐like polymers is still of interest in the aim of investigating their physicochemical properties. For this purpose, poly(3,4‐dimethyl maleic imidoethyl acrylate)‐block‐polybutadiene‐block‐poly(3,4‐dimethyl maleic imidoethyl acrylate) triblock copolymer is synthesized in a convergent manner using a combination of living polymerization (anionic polymerization), reversible deactivation radical polymerization, and click chemistry. This copolymer is self‐assembled in a selective solvent (heptane/THF mixture) of the polybutadiene block leading to the formation of flower‐like micelles in thermodynamic equilibrium in dilute solution. These resulting transient architectures are fixed by covalently crosslinking the micelles core by inducing [2+2] cyclodimerization of the 3,4‐dimethyl maleic imidoethyl groups borne by the short solvophobic blocks under UV irradiation. Single flowers are isolated from residual non‐crosslinked chains by semipreparative size exclusion chromatography (SEC) and characterized by 1H NMR, SEC, dynamic light scattering (DLS), and transmission electron microscopy (TEM).
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.
A series of random binary poly(ethylene glycol) and fluoropolymer brushes (POEGMA‐PNCA‐F15) are grafted onto substrates via surface‐initiated polymerizations (atomic transfer radical polymerization and ring opening metathesis polymerization, respectively) from polydopamine based mix‐catecholic initiators. The chemical composition, surface morphology, swellability, and wettability of the as‐prepared surfaces are characterized by X‐ray photoelectron spectra (XPS), atomic force microscopy (AFM), and static water contact angle measurements, respectively. The antifouling properties are evaluated by settlement of spores and diatoms, the results indicate that the as‐prepared amphiphilic surfaces with random hydrophilic and hydrophobic polymer brushes can mitigate biofouling, and the ratio of the hydrophilic and hydrophobic polymer brushes is a key determinant factor in antifouling effect, the optimal ratio (1:1 initiator) of bipolymer brushes on surfaces exhibits good antiadhesion performance against both Chlorella spores and Navicula diatoms.
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.
A new method is developed to synthesize organic microsphere‐supported polymer brushes for affinity separation of saccharides and glycoproteins. In the first step, crosslinked polymer microspheres are synthesized using atom transfer radical polymerization (ATRP). The terminal ATRP initiators on the microspheres are used to graft polymer brushes from propargyl acrylate and N‐isopropyl acrylamide. The microsphere‐supported polymer brushes are conjugated with an azide‐tagged phenylboronic acid to complete the material synthesis. The microsphere‐supported, boronic acid‐containing polymer brushes are able to bind not only low molecular weight cis‐diol compounds but also glycoproteins. The synthetic procedure developed in this work provides a convenient means for preparing all‐organic microsphere‐supported polymer brushes that have high alkaline stability. Using the surface‐attached polymer brushes to immobilize a catalytic glycoprotein (horseradish peroxidase), it is possible to retain on‐particle enzyme activity due to the open structure of the polymer brushes and the oriented immobilization.
Block copolymer phase separation has been employed to form templates for the fabrication of nanoscale patterns of metals due to their characteristic size scales that range from several nanometers to tens of nanometers. In the present work, poly(vinyl catechol‐block‐styrene) PVCa‐b‐PSt synthesized with various compositions forms unique microphase‐separated structures. Silver nanoparticles are spontaneously formed inside of the PVCa phases due to the reductive properties of the catechol moieties. The alignment and formation of silver nanoparticle arrays is successfully achieved without the need for high‐temperature thermal treatment or chemical reduction processes. The present system can be applied to the formation of nanoparticle arrays with a wide variety of metals by control of their arrangement.
In this paper, “star anise”‐like anisotropic micelle (AM) from direct aqueous self‐assembly of poly(ethylene oxide)‐block‐poly(p‐dioxanone) amphiphilic diblock copolymer is presented. By adding poly(ethylene imine) (PEI), the AM shows morphological change from “star anise” to swollen sphere. The mechanism of PEI‐triggered morphological transition involving complexation and weakening of crystallizability is revealed.
A series of highly branched star‐comb poly(ε‐caprolactone)‐block‐poly(l ‐lactide) (scPCL‐b‐PLLA) are successfully achieved using star‐shaped hydroxylated polybutadiene as the macroinitiator by a simple “grafting from” strategy. The ration of each segment can be controlled by the feed ratio of comonomers. These star‐comb double crystalline copolymers are well‐defined and expected to illustrate the influences of the polymer chain topology by comparing with their counterparts in linear‐shaped, star‐shaped, and linear‐comb shape. The crystallization behaviors of PCL‐b‐PLLA copolymers with different architectures are investigated systematically by means of wide‐angle X‐ray diffraction, differential scanning calorimetry, and polarized optical microscopy analysis. It is shown that the comb branched architectures promote the crystallization behavior of each constituent significantly. Both crystallinity and melting temperature greatly raise from linear to comb‐shaped copolymers. Compared to linear‐comb topology, the star‐comb shape presents some steric hindrance of the graft points, which decrease the crystallinity of scPCL‐b‐PLLA. Effects of copolymer composition and chain topology on the crystallization are studied and discussed.
Dendrigraft poly(l ‐lysine) (DGL) polyelectrolytes, obtained by iterative polycondensation of N‐trifluoroacetyl‐l ‐lysine‐N‐carboxyanhydride, constitute very promising candidates in many biomedical applications. In order to get a better understanding of their structure–property relationships in these applications, their absolute average molecular weights have to be accurately measured. Size‐exclusion chromatography coupled to a multi‐angle laser‐light‐scattering detector (SEC‐MALLS) is known to be the most appropriate analytical tool. These measurements require the determination of the refractive index increment, dn/dc, of these highly branched polycationic macromolecules in aqueous solution. This optical property has to be measured in the same aqueous conditions as SEC‐MALLS eluents. Consequently, data are determined and discussed as a function of different aqueous SEC‐MALLS eluents, as well as different counter‐ions of the many ammonium groups of DGL (generation 3, DGL‐3, used as a model herein). The resulting number‐average molecular weights, , are found to be very dissimilar when the measured dn/dc values are directly considered. In contrast, very close values are obtained (average = 18 700, standard error of 1110 g mol?1) with a low coefficient of variation for such data (ca. 6% for six analyses), when the dn/dc are corrected by the exact lysine amount (measured by the total Kjeldahl nitrogen method).
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.
Core–corona inversion of micelles of diblock copolymer poly(acrylic acid)‐block‐poly(N‐isopropylacrylamide) (PAA‐b‐PNIPAM), has been successfully realized by switching either pH or temperature. The strong interaction of doxorubicin with the PAA block and the pH‐sensitive drug release from the polymer make the system very useful as a controlled drug delivery system. The encapsulation of hydrophobic Nile Red molecules above the lower critical solution temperature of PNIPAM suggests that this polymer may be useful for removing hydrophobic pollutants.
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 size exclusion chromatography (SEC)‐gradient method is developed allowing poly(n‐butyl acrylate‐stat‐acrylic acid)s to be separated with respect to content of acrylic acid over the complete composition range. After setting up the chromatographic method, samples that, according to the amounts of charged monomers, are expected to have identical chemical composition are compared. The chromatograms reveal differences in elution volume, which, by 1H NMR spectroscopy, can be partially traced back to differences in polymer composition. In addition, samples of similar compositions prepared in different solvents exhibit differences in chemical composition distribution.
The cationic polymerization of 1,3‐pentadiene using a tert‐butyl chloride (tBuCl)/TiCl4 initiating system in CH2Cl2 at different reaction conditions is reported. It is shown that the reaction rate increases with the increase of the tBuCl/TiCl4 molar ratio, while the molecular weight distribution becomes narrower. Well‐defined oligo(1,3‐pentadiene)s ( ≤ 3500 g mol?1; / ≤ 3.0) are obtained at high tBuCl/TiCl4 molar ratio (340) and low temperature (–78 °C). 1H and 13C NMR spectroscopy studies reveal the presence of tert‐butyl head and –CH2–Cl end groups. The number‐average functionalities (Fns) at the α‐ and ω‐ends are calculated to be Fn(tBu) > 1 and Fn(Cl) < 1, respectively. The general mechanism of 1,3‐pentadiene polymerization is proposed.
Copolymerization of carbon dioxide (CO2) and propylene oxide (PO) is employed to generate amphiphilic polycarbonate block copolymers with a hydrophilic poly(ethylene glycol) (PEG) block and a nonpolar poly(propylene carbonate) (PPC) block. A series of poly(propylene carbonate) (PPC) di‐ and triblock copolymers, PPC‐b‐PEG and PPC‐b‐PEG‐b‐PPC, respectively, with narrow molecular weight distributions (PDIs in the range of 1.05–1.12) and tailored molecular weights (1500–4500 g mol?1) is synthesized via an alternating CO2/propylene oxide copolymerization, using PEG or mPEG as an initiator. Critical micelle concentrations (CMCs) are determined, ranging from 3 to 30 mg L?1. Non‐ionic poly(propylene carbonate)‐based surfactants represent an alternative to established surfactants based on polyether structures.
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.
Herein the synthesis of core cross‐linked (CCL) mixed micelles through a UV‐promoted thiol–ene addition onto lipid core unsaturations and the subsequent release of an encapsulated drug depending on the external conditions (pH/temperature) are reported. The thiol–ene addition proceeds even in the absence of a photoinitiator to reach a complete conversion in a few minutes in bulk. The cross‐linking reaction is applied in aqueous media onto lipid‐b‐poly(acrylic acid) (lipid‐b‐PAA) only and then a mixture of pH‐sensitive lipid‐b‐PAA and thermo‐sensitive lipid‐block‐poly(2‐isopropyl‐2‐oxazoline) copolymers. Structurally CCL micelles, preserved in any conditions, with a stimuli‐sensitive corona whose swelling depends on the external pH or/and temperature, are successfully prepared. The release of vitamin K1 (VK1) is then investigated from all the previous systems and demonstrates a strong dependency to the external conditions. Indeed, the dual‐sensitive CCL micelles release VK1 only when two triggers (pH 10 and T = 38 °C) are simultaneously activated.
Nanomaterial with variable d‐spacing is prepared by hydrolysis of a bulk self‐assembly with lamellar morphology. The bulk self‐assembly is prepared from a disulfide‐containing polystyrene–(S2)poly(tert‐butyl acrylate)–polystyrene (PS–(S2)PtBA–PS) triblock copolymer, which is polymerized via two‐step atom transfer radical polymerization (ATRP) with a disulfide‐containing difunctional initiator. The results show that the PS–(S2)PtBA–PS with 47.6% weight fraction of PS bulk self‐assembles into ordered nanomaterial with lamellar morphology. As the morphology of the bulk material is fixed by glassy PS microdomains, the PtBA domains can be hydrolyzed to poly(acrylate acid) (PAA) domains in the bulk state of PS and then the d‐spacing can be regulated like an accordion by changing the environment of the material. Also, the hydrolyzed self‐assembly can be applied as a template to load nanoparticles in PAA microdomains to prepare layered inorganic/organic composites. The bulk material can be dispersed in methanol to form dispersed (multilayered) nanoplates by cleaving the disulfide bonds by tributylphosphine (Bu3P) reduction. Moreover, the ester bonds in the hydrolyzed bulk material can be cleaved by NaOH, and then water‐dispersed (multilayered) nanoplates with pH responsivity are obtained.
Six poly(phenylene‐alt‐dithienobenzothiadiazole)‐based polymers have been synthesized for application in polymer–fullerene solar cells. Hydrogen, fluorine, or nitrile substitution on benzothiadiazole and alkoxy or ester substitution on the phenylene moiety are investigated to reduce the energy loss per converted photon. Power conversion efficiencies (PCEs) up to 6.6% have been obtained. The best performance is found for the polymer–fullerene combination with distinct phase separation and crystalline domains. This improves the maximum external quantum efficiency for charge formation and collection to 66%. The resulting higher photocurrent compensates for the relatively large energy loss per photon (E loss = 0.97 eV) in achieving a high PCE. By contrast, the polymer that provides a reduced energy loss (E loss = 0.49 eV) gives a lower photocurrent and a reduced PCE of 1.8% because the external quantum efficiency of 17% is limited by a suboptimal morphology and a reduced driving force for charge transfer.
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