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 efficient way for covering various surfaces with poly(lactic acid) (PLA) is discussed. In a first step, the material is coated with polydopamine (PDA) by air oxidation of dopamine. The resulting PDA layer acts as an initiator for ring‐opening polymerization (ROP) of lactide resulting in an outer PLA shell. Since PDA sticks to almost every solid material, the methodology has a wide scope. The strategy is demonstrated with magnetic nanoparticles and non‐magnetic powders.
Copolymerization of ethylene with 4‐penten‐1‐ol (4P1O) is conducted by using a half‐titanocene catalyst. The incorporation of 4P1O is high as approximately 10 mol%. The assignments of the 13C NMR spectrum and the analysis of the sequence distribution show the existence of not only the alternative structure but also the repeated 4P1O units. The product of the reactive ratios is calculated as ca. 2.
Unsaturated polyesters are synthesized via ring‐opening copolymerization of α‐methylene‐δ‐valerolactone and δ‐valerolactone. These polyesters 4a–c are mixed with ethyl methacrylate (EMA), 2‐hydroxyethyl methacrylate (HEMA), and α‐methylene‐δ‐valerolactone (α‐MVL), respectively. Then, crosslinking is carried out by free radical polymerization initiated by an azo‐initiator. A second glass transition is found with incorporation of HEMA and α‐MVL. These findings indicate the formation of phase‐separated polyester blocks crosslinked with the poly(meth)‐acrylic‐segments, respectively poly(α‐methylene‐δ‐valerolactone) segments.
An N‐vinylimidazole‐based monomer carrying an adamantyl group, (1‐vinyl‐2‐yl)methyladamantan‐1‐ylcarbamate ( 3 ), is synthesized. The terpolymerization with N‐vinylimidazole ( 4 ) and 1‐vinyl‐2‐(hydroxymethyl)imidazole ( 2 ) yields terpolymers ( 5a–b ) with high upper critical solution temperature (UCST)‐type transitions in water. The solubility can be influenced by the addition of various amounts of randomly methylated β‐cyclodextrin (RAMEB‐CD). It is found that supramolecular host/guest interaction clearly controls the solution behavior.
Thermally reduced graphene modified with cationic ammonium ions (AAG)—affording a stable dispersion in water—self‐assembles well by electrostatic interaction on the surface of anionic poly(methyl methacrylate) (PMMA) particles of various sizes, by simple mixing in water. An interconnected 3D electrically conductive network of AAG is effectively generated in the composite when the self‐assembled composite is compression molded. The AAG network becomes wide‐meshed and electrical conduction is improved when the PMMA particle size increases, exhibiting a percolation threshold of electrical conductivity as low as 0.06 vol%. In contrast, the protection of PMMA from oxidation by air is more effective when the network is fine‐meshed.
The variation of the drift mobility of positive and negative charge carriers in films of anthracene‐containing poly(p‐phenylene‐ethynylene)‐alt‐poly(p‐phenylene‐vinylene)s ( AnE‐PVs ), differently substituted, is investigated as a function of the applied electric field. Branched 2‐ethylhexyl and linear alkoxy side chains of different lengths are considered, as well as well‐defined and random distributions of lateral substituents. The same conditions are used both for the deposition of the polymer films and for their characterization, which allows for the establishment of a clear relationship between the chemical structure and the charge carrier mobility.
Polymer blends play a significant role in polymer science due to their new and unique properties compared with the individual polymer components. However, most polymer blends are immiscible and not adaptive to environmental stimuli. Here, an enhancement of the compatibility of an immiscible poly(methy acrylate)/polystyrene blend based on multiple‐responsive benzo‐21‐crown‐7/dialkylammoniumsalt host–guest interactions is made. Owing to the multi‐responsiveness and reversibility of benzo‐21‐crown‐7/dialkylammoniumsalt host–guest interactions, the polymer blend recovers its compatibility after being damaged by environmental factors, indicating its adaptiveness.
Novel branched polyoxymethylene copolymers are synthesized by cationic copolymerization of 1,3,5‐trioxane (TOX) with 3‐(alkoxymethyl)‐3‐ethyloxetane (ROX) using BF3·Et2O as an initiator. Four oxetane derivatives with different side‐chain lengths (from 1 to 6 carbons) are tested for copolymerization. The copolymer composition is controlled by the feed ratio of ROX, and influenced by the chain length of alkyl group on ROX. The incorporation ratio and side‐chain length of the ROX unit have great influence on the thermomechanical properties and crystallinity of the copolymers.
The thermostable α‐glucan phosphorylase‐catalyzed enzymatic α‐glucuronylation and subsequent α‐glucosaminylation of glycogen using α‐d ‐glucuronic acid 1‐phosphate (GlcA‐1‐P) and α‐d ‐glucosamine 1‐phosphate (GlcN‐1‐P), respectively, produce amphoteric glycogens. The products exhibit the inherent isoelectric points, which change depending on the GlcA/GlcN ratios. Chain elongation of amyloses from the nonfunctionalized, nonreducing ends of the products through the thermostable α‐glucan phosphorylase‐catalyzed enzymatic polymerization of α‐d ‐glucose 1‐phosphate monomers is demonstrated to yield amphoteric glycogen hydrogels. The produced hydrogels exhibit pH‐responsive behavior.
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.
The synthesis of three different electron‐deficient internal alkynes for the metal‐free 1,3‐dipolar azide–alkyne cycloaddition is shown. The alkynes are polymerized with several multifunctional azides and the reaction enthalpy (ΔH) is investigated by differential scanning calorimetry (DSC). The mechanical properties of the resulting polymers are analyzed using nanoindentation. The polymerization results in hard materials with an E‐modulus of maximum 2.5 GPa, which make them interesting in particular for biomedical applications.
Functional hybrid materials with optically active metal‐ligand moieties embedded within a polymer matrix have a great potential in (bio)materials science, including applications in light‐emitting diode devices. Here, a simple strategy is reported to incorporate terpyridine derivatives into the side chains of elastin‐like polymers (ELPs). The further binding of trivalent lanthanide ions with the terpyridine ligands generates an array of photoluminescence ranging from the visible to the near‐infrared regions. As thin films, these ELP‐based optical materials also exhibit distinct morphologies that depend upon the temperature of the aqueous solutions from which the hybrid polymers are spin coated or drop cast.
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.
The consideration of polyaniline (PANI) as a supramolecular assembly similar to J‐aggregates of dyes is proposed. Fibrils with a length of more than 100 nm and a diameter of about 4 nm are formed in water during aniline polymerization, as shown by small‐angle X‐ray scattering. Long‐wavelength absorption of the fibrils, red‐shifted with respect to highly crystalline PANI film supports the idea about the formation of J‐aggregates. Their formation, similar to dyes, is promoted by the addition of a sulfonated polyelectrolyte and becomes more pronounced with an increase of the molar mass of the polyelectrolyte. Self‐organization of aniline oligomers in a polar environment is confirmed by atomistic molecular dynamics simulations.
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%).
Highly monodisperse poly(2‐hydroxyethyl acrylate)‐grafted poly(methyl methacrylate) (PMMA) microspheres are prepared by a facile photoinitiated dispersion polymerization in ethanol/water mixtures at room temperature. Poly(2‐hydroxyethyl acrylate) homopolymers with different molecular weights are synthesized via reversible addition‐fragmentation chain transfer (RAFT) solution polymerization and employed as steric stabilizers in photoinitiated dispersion polymerization. The effect of macro‐RAFT agent (both concentration and molecular weight) on particle diameter is studied in detail. Kinetic study indicates that the polymerization proceeded rapidly with 96% yield being reached with 1 h of UV irradiation. Finally, the obtained hydroxyl‐rich PMMA microspheres are used as building blocks for the preparation of covalently cross‐linked colloidosomes.
Donor–acceptor alternating copolymers with chlorine atoms on the backbone are synthesized via a straightforward Stille polycondensation. Thiophene and chlorine‐substituted 2,3‐diphenylquinoxaline are chosen as the donor and acceptor moieties, respectively. Compared with the corresponding non‐substituted and fluorine‐substituted analogues, which are also synthesized for systematical studies, the chlorine‐bearing copolymer exhibits the deepest lowest unoccupied molecular orbital (LUMO). The highest occupied molecular orbital (HOMO) level of the chlorine‐bearing copolymer can be modified by applying different donor moieties. Additionally, these chlorine‐bearing copolymers show low self‐absorption and large Stokes Shift.
Trithiocarbonate end‐functionalized poly(N‐acryloylglycinamide) (PNAGA), synthesized via reversible addition–fragmentation transfer (RAFT) polymerization of different molecular weights, is grafted onto gold nanoparticles (AuNPs) by ligand exchange in phosphate‐buffered saline. The PNAGA‐grafted AuNPs display upper critical solution temperature (UCST)‐type transitions: stable colloidal distribution and aggregation above and below the cloud points, respectively. Cloud points of PNAGA are not affected by the grafting procedure, and PNAGA@AuNPs show similar cloud points as that of the trithiocarbonate end‐functionalized free‐PNAGAs used for grafting. The UCST‐type phase transition is reversible for many cycles. The reversible control of the phase transition is proved by turbidity measurements and UV–vis spectroscopy, as well as by transmission electron microscopy (TEM).
A series of ZrIV and TiIV complexes containing the 6‐(2‐(diethylboryl)phenyl)pyridyl‐2‐yl motif are used in the methylalumoxane‐triggered copolymerization of ethylene (E) with norborn‐2‐ene (NBE). 13C NMR analyses reveal that vinyl insertion polymerization (VIP)‐derived poly(E)‐co‐poly(NBE) is obtained with pre‐catalysts 1–4 and 6 , while pre‐catalyst 5 allows for the synthesis of a copolymer that contains both VIP‐ and ring‐opening metathesis polymerization (ROMP)‐derived structures. All the VIP‐derived poly(E)‐co‐poly(NBE) sequences show predominantly isolated NBE/alternating‐syndiotactic E‐NBE, as well as alternating‐isotactic E‐NBE sequences. The microstructure of the copolymers is correlated with the propensity of the pre‐catalysts to allow tandem ROMP‐VIP.
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