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.
Flame‐retardant polypropylene (PP)/carbon nanotubes (CNTs) nanocomposites influenced by surface functionalization and surfactant molecular weights are studied. 3‐Aminopropyl‐triethoxysilane (APTES) is utilized to modify the CNTs (f‐CNTs), and maleic‐anhydride‐grafted PP (MAPP) with two molecular weights ( of 800 and 8000 g mol?1) is used to further improve the dispersion of f‐CNTs in the PP matrix. Thermal gravimetric analysis (TGA) and microscale combustion calorimetry (MCC) reveal that the molecular weight of MAPP directly affects the thermal stability and flammability of PP/f‐CNTs PNCs: both MAPP polymers ( of 800 and 8000 g mol?1) increase the thermal stability of PP; however, the heat release rate of PP/f‐CNTs is reduced in the presence of MAPP ( of 800 g mol?1) and increased in the presence of MAPP ( of 8000 g mol?1). MAPP ( of 800 g mol?1) also results in a lower viscosity of the PP/f‐CNTs PNCs compared with pure PP.
l ‐lactide or meso‐lactide are polymerized either at 120 °C where the polymerization process of l ‐lactide is accompanied by crystallization, or at 180 °C where poly(l ‐lactide) remains in the molten state. Polymerizations at 120 °C initially yield even‐numbered chains (with respect to lactic acid units) having relatively low dispersity, but the fraction of odd‐numbered chains increases with time and the entire molecular weight distribution changes. Traces of cyclics are only formed after 7 d. Polymerizations at 180 °C yield equilibrium of even and odd‐numbered chains from the beginning, but at low monomer/initiator ratios and short reaction times (<4 h) cyclics are again not formed. They appear at longer reaction times and entail higher dispersities. The results are discussed in terms of five different transesterification mechanisms.
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.
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.
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).
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.
Three perylene‐containing conjugated microporous polymers (PrCMPs) are synthesized via Suzuki–Miyaura cross‐coupling reaction from perylene with four polymerizable functional groups and a range of different substituted benzene derivatives. The pore property and bandgap of the resulting PrCMPs can be tuned by changing the comonomer of benzene with different substituted groups and positions. The photocatalytic performances of the polymers are highly dependent on the surface area, geometry, and bandgap of the PrCMPs. It was found that the 1,2,4,5‐linked polymer of PrCMP‐3 shows the highest hydrogen evolution rate (HER) of 12.1 µmol h−1 under UV–vis light irradiation among the three polymers because of its high surface area, broad light absorption, and suitable bandgap. PrCMP‐3 also exhibits good photocatalytic stability for prolonged hydrogen production reaction. This result demonstrates that the crucial role of the linkage geometry offers a general principle for the rational design of conjugated microporous polymer photocatalysts.
Two triblock copolymers, polybutadiene‐block‐poly(ε‐caprolactone)‐block‐poly(methyl methacrylate) (PBD‐b‐PCL‐b‐PMMA) and polybutadiene‐block‐poly(ε‐caprolactone)‐block‐polystyrene (PBD‐b‐PCL‐b‐PS), are synthesized by combination of coordinative chain transfer polymerization (CCTP), ring‐opening polymerization (ROP), and atom transfer radical polymerization (ATRP). The molecular structures of these polymers are determined by 1H NMR and gel‐permeation chromatography (GPC) analysis. The resulting triblock copolymers are evaluated as compatibilizing agents for highly immiscible binary PBD/PMMA and PBD/PS blends. The presence of these compatibilizers substantially reduces the average PMMA or PS droplet size. Furthermore, static water contact angle experiments are employed to assess the modification of the surface properties of nonpolar PBD.
Recent advances in synthetic methodologies have brought us closer than ever to the precision conferred by nature. For example, the control possible in reversible deactivation radical polymerization enables us to design and synthesize macromolecules with unprecedented control over not only the polymer chain ends, but also the side chain functionality. Furthermore, this functionality can be exploited to afford chemical modification of peptides and proteins, with ever‐improving site‐specificity, yielding a range of well‐defined protein/peptide‐hybrid materials. Such materials benefit from the amalgamation of the properties of proteins/peptides with those of the synthetic (macro)molecules in question. Here, the latest developments in the synthesis of functional polymers and their use for preparation of well‐defined protein/peptide‐polymer conjugates will be discussed, with particular attention focused on modulating the stability, efficacy and/or administration of therapeutic peptides.
The application of selenol‐X chemistry in nucleophilic substitution and Se‐Michael addition reactions for polymer chain end modification is presented. Selenol‐labeled polystyrene can easily react with alkyl halides, methyl methacrylate, methyl acrylate, pentafluorostyrene, etc. The mild conditions make it attractive for the synthesis of macromonomers. The resulting polymers are analyzed and characterized by UV, size‐exclusion chromatography (SEC), NMR, and matrix assisted laser desorption/ionization time of flight mass spectroscopy.
Here, the synthesis, characterization, and photovoltaic properties of four new donor–acceptor copolymers are reported. These copolymers are based on 4,4‐difluoro‐cyclopenta[2,1‐b:3,4‐b′] dithiophene as an acceptor unit and various donor moieties: 4,4‐dialkyl derivatives of 4H‐cyclopenta[2,1‐b:3,4‐b′]dithiophene and its silicon analog, dithieno[3,2‐b:2′,3′‐d]‐silol. These copolymers have an almost identical bandgap of 1.7 eV and have a HOMO energy level that varies from ?5.34 to ?5.73 eV. DSC and X‐ray diffraction (XRD) investigations reveal that linear octyl substituents promote the formation of ordered layered structures, while branched 2‐ethylhexyl substituents lead to amorphous materials. Polymer solar cells based on these copolymers as donor and PC61BM as acceptor components yield a power conversion efficiency of 2.4%.
Ethylene–1‐hexene copolymer materials, ranging from semicrystalline linear low‐density polyethylene (LLDPE) to completely amorphous polyethylenes (PEs), are prepared from ethylene alone in a single reactor by the tandem polymerization of bis(2‐dodecylsulfanyl‐ethyl)amine–CrCl3 (SNS–Cr) and (N‐tert‐butylamido) (tetramethylcyclopentadienyl)–titanium dichloride (CGC–Ti) at 75 °C and under atmospheric pressure. The polymerization activities are on the order of 105–106 g (mol Ti)?1 h?1. 1‐Hexene incorporation in the resulting copolymers can be adjusted by varying the Cr–Ti molar ratio and/or applying a short period of pre‐trimerization. Copolymers with high 1‐hexene incorporation up to 15 mol% are obtained. Few vinyl and vinylene chain ends are detected by 13C NMR, suggesting that 1‐hexene does not act as a chain‐transfer agent. Narrow molecular‐weight distributions with polydispersities from 1.9 to 2.6 are obtained, characteristic of a single‐active‐site nature of the catalyst system.
Graft polymers with poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) as backbones are successfully prepared via two convenient steps. The utilization of semiflexible PPO as backbones offers unique properties for the graft polymers. Thermal, rheological, and phase behaviors of these new graft polymers are well controlled via the precise design of architectural parameters. The disordered microphase separation in melt state and the proper composition of side grafts provide the ease of thermal processing for these graft polymers. The graft density shows impact on the relaxation and mechanical properties of the thermoplastics. This work shows the possibility to use lots of semiflexible engineering polymers as backbones to construct new thermoplastics.
A general route for the controlled functionalization of polyferrocenylsilane‐block‐polyvinylsiloxane copolymers, which should be transferable to other silicone‐based materials, is developed utilizing the photoinitiated thiol‐ene reaction. Poly(ferrocenyldimethylsilane)54‐block‐poly(methylvinylsiloxane)510 (PFDMS54‐b‐PMVS510) is synthesized via sequential living anionic polymerization and quantitatively functionalized with a range of thiols, with the aim of tuning the solubility of the resulting materials for self‐assembly studies or incorporating more complex functionality for subsequent applications. When functionalization is attempted using a deficit of thiol, the photoinitiator 2,2‐dimethoxy‐2‐phenylacetophenone, used to accelerate the radical reaction, is found to cause significant cross‐linking of the polysiloxane chain. Reproducible percentage thiol‐ene functionalization of the polysiloxane block can be achieved by the use of PFDMS53‐b‐PMVS58/PDMS444 (PDMS = polydimethylsiloxane), prepared by the copolymerization of cyclic siloxane monomers, [Me(CH?CH2)SiO]3 and [Me2SiO]3, to tune the vinyl group incorporation pre‐functionalization.
Hybrid composites with highly ordered structures show promise for applications in various fields and thus there is great interest in their fabrication. In this context, Janus nanoparticles (JNPs) are synthesized with the aim of further incorporating them into polystyrene‐block‐poly(2‐vinylpyridine) (PS‐b‐P2VP) block copolymers to fabricate hybrid composites. It is observed that the dispersed JNPs are located at the boundary of the two morphological phases in PS‐b‐P2VP. The orientation of the lamellar structure in the bottom and free surface region of the block copolymer (BCP) composites shows a distinct difference as the composition of the JNPs is adjusted. The processing conditions of the nanoparticle/BCP composites are found to play an important role in achieving the desired structures.
In the context of novel sustainable and structurally significant building blocks for polymer science, the synthetic routes are described to new oligoamide structures based on the terpenoid ketone (?)‐menthone. The basic concept is an oxime formation of this cyclic ketone followed by the Beckmann rearrangement, resulting in the corresponding lactams. These lactams are polymerized under anionic or acid‐catalyzed conditions (ring‐opening polymerization (ROP)) to give alkyl‐substituted and stereocenter containing oligoamide scaffolds that are assumed to be suitable for further copolymerizations and modifications and thus for a wide range of different applications. The regio‐ and the stereochemistry of the formed oximes and lactams as well as their impact on the polymerization behavior is discussed.
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.
Cationic polyelectrolytes find potential applications in electronic device fabrication, biosensing as well as in biological fields. Herein, a series of cationic main‐chain polyelectrolytes with pyridinium‐based p ‐phenylenevinylene units that are connected via alkylene spacers of varying lengths are synthesized by a base‐catalyzed aldol‐type coupling reaction. Their mean average molecular weights range from 15 000 to 32 000 g mol‐1, corresponding to about 16–33 repeat units. Due to the presence of alkyl side‐chains and alkylene spacers as well as cationic hard‐charges the polymers are endowed with amphiphilic character and hence, aggregation of these polyelectrolytes at high concentration leads to thermoreversible physical gel formation in dimethyl sulfoxide accompanied by interchain interactions. Morphological analysis shows spherical aggregates in case of C16‐Poly‐S12 in dimethyl sulfoxide. Dependence of gelation behavior on the length of alkyl side‐chains and alkylene spacers of the polyelectrolytes are addressed.
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