Linear Copolymers Research Articles

Tailored silyl ether monomers enable backbone-degradable polynorbornene-based linear, bottlebrush and star copolymers through ROMP.

Ring-opening metathesis polymerization (ROMP) of norbornene-based (macro)monomers is a powerful approach for the synthesis of macromolecules with diverse compositions and complex architectures. Nevertheless, a fundamental limitation of polymers prepared via this strategy is their lack of facile degradability, which limits their utility in a range of applications. Here, we describe a class of readily available bifunctional silyl-ether-based cyclic olefins that copolymerize efficiently with norbornene-based (macro)monomers to provide copolymers with backbone degradability under mildly acidic aqueous conditions and degradation rates that can be tuned over several orders-of-magnitude depending on the silyl ether substituents. These monomers can be used to manipulate the in vivo biodistribution and clearance rate of PEG-based bottlebrush polymers, as well as to synthesise linear, bottlebrush, and brush-arm star copolymers with degradable segments. We expect that this work will enable preparation of degradable polymers by ROMP for biomedical applications, responsive self-assembly, and improved sustainability.

Synthesis of a Smart Conductive Block Copolymer Responsive to Heat and Near Infrared Light.

A method for the synthesis of a linear block copolymer (PNIPAM-b-PANI), containing a thermoresponsive block (poly(N-isopropylacrylamide), PNIPAM) and a Near Infrared (NIR) light-absorbing block (polyaniline, PANI), is reported. The synthetic approach involves a two-step successive polymerization reaction. First, the radical polymerization of NIPAM is done using 4-aminothiophenol as a chain transfer agent for the obtention of thermosensitive block terminated with an aniline (ANI) moiety. Second, the oxidative polymerization of ANI is initiated in ANI moiety of thermosensitive block to grow the second conductive PANI block. 1H nuclear magnetic resonance (NMR) and FT-IR spectroscopy shows the characteristics peaks of both polymeric blocks revealing the successful copolymerization process. Static Light Scattering (SLS) and UV-Visible combined measurements allowed the determination of the Mw for PNIPAM-b-PANI macromolecule: 5.5 × 105 g mol−1. The resulting copolymer is soluble in water (8.3 g L−1) and in non-aqueous solvents, such as ethanol, formic acid, acetonitrile, and others. Both polymer blocks chains show the properties of the polymer chains. The block copolymer shows a lower critical solution temperature (LCST) at the same temperature (32–34 °C) than PNIPAM, while the copolymer shows pH dependent UV-vis-NIR absorption similar to PANI. The PNIPAM block suffers a coil to globule transition upon NIR light irradiation (785 nm, 100 mW), as shown by turbidimetry and Atomic Force Microscopy (AFM), due to local heating (more than 9 °C in 12 min) induced by the NIR absorption at the PANI block. Furthermore, the electrical conductivity of PNIPAM-b-PANI thin films is demonstrated (resistivity of 5.3 × 10−4 Ω−1 cm−1), indicating that the PANI block is present in its conductive form.

An Organosilicon Composition for Protection of Active Components of Electronic Products

A two-component organosilicon composition was developed based on a solution of linear ladder organosilicon block copolymers containing linear polyorganosiloxane and ladder phenylsilsesquioxane units in an organic solvent and a curing agent, vinyl-tris-(acetoximo)silane. The composition can be used for the preparation of heat-resistant flexible and strong electroinsulating corrosion-passive coatings that serve to protect active components of micro- and radioelectronic products from effects of severe climatic factors.

Fractional yield and phase separation of ladder-like interpolymer complexation between diblock copolymers

We analyze the fractional yield and the phase separation of the ladder-like interpolymer complexation reaction between two diblock copolymers A1A2 and B1B2 forming a linear triblock copolymer A1DB1, i.e., A1A2+B1B2⇌A1DB1. The study is carried out by using the self-consistent field theory coupled with the interpolymer-complexation model of the chemical reactions. The fractional yield of the complexation (φ3/φ), defined as the equilibrium volume fraction of the triblock copolymers, can be improved via several approaches including increasing the secondary bonding energy εZD and enhancing the solvent selectivity to the triblock copolymer A1DB1. The strong solvent selectivity and the chemical incompatible interaction between the diblock copolymers and the triblock copolymers make the homogenous phase unstable. The phase separated state D/S emerges between the sigle-stranded-diblock-dominated phase S and the duplex-triblock-dominated phase D. With the fixed length of the diblock copolymers, the length of the complex block D influences the subtle balance among several contributions to the free energy including the bonding energy, the conformational entropic loss due to complexation, the solvent selectivity, and the interaction between the polymers.

100 Micrometer bore open tubular capillary column modified with linear co-polymer chains for application in low pressure liquid chromatography

The performance of a 100 um i.d. open tubular column modified with linear co-polymer chains has been explored under low pressure operating conditions. A 512 mm fused-silica capillary was reacted with 3-chloropropyl isocyanate followed by sodium diethyldithiocarbamate. A copolymer layer was then immobilized on the inner surface via reversible addition-fragmentation transfer polymerization of styrene, methacrylic acid and N-phenylacrylamide. The thickness of the polymer layer was ca 1.5 µm. The column was evaluated for the separation of a mixture composed of three peptides (Trp-Gly, angiotensin I, bradykinin). The number of theoretical plates (N) as high as 72,100 plates/column (corresponding to 140,800/m, 7.10 µm plate height) was achieved. The column to column and day to day reproducibility of our columns was found better than 2.1%. For comparison purpose, similar chromatographic data for a selected analyte was also obtained with a commercial microcolumn of 0.5 mm id packed with a conventional C18 phase (5 µm), and 17 µm was the plate height obtained at the optimum flow rate. The van Deemter plots and kinetic plots were also obtained for comparison between our open tubular capillary column and the commercial packed column of a narrow id.

Supramolecular Competitive Host-Guest Interaction Induced Reversible Macromolecular Metamorphosis.

In this work, a rational strategy of competitive host-guest complexation between dioxynaphthalene (Naph) and tetrathiafulvalene (TTF) subunits as guests and cyclophane cyclobis(paraquat-p-phenylene) (CBPQT4+ ) module as host is exploited to modify the macromolecular architecture, so-called supramolecular metamorphosis, in aqueous media. The architectures of the polymers can be reversibly transformed from a linear diblock copolymer AB to a linear AC block copolymer or from a linear block copolymer to a comb copolymer by redox switching. Interestingly, as TTF- and Naph-based complexes feature different characteristic colors, it offers a great opportunity to directly observe nanoscaled macromolecular metamorphosis of materials with the naked eye.

Structure and Dynamics of Thermosensitive pDNA Polyplexes Studied by Time-Resolved Fluorescence Spectroscopy.

Combining multiple stimuli-responsive functionalities into the polymer design is an attractive approach to improve nucleic acid delivery. However, more in-depth fundamental understanding how the multiple functionalities in the polymer structures are influencing polyplex formation and stability is essential for the rational development of such delivery systems. Therefore, in this study the structure and dynamics of thermosensitive polyplexes were investigated by tracking the behavior of labeled plasmid DNA (pDNA) and polymer with time-resolved fluorescence spectroscopy using fluorescence resonance energy transfer (FRET). The successful synthesis of a heterofunctional poly(ethylene glycol) (PEG) macroinitiator containing both an atom transfer radical polymerization (ATRP) and reversible addition–fragmentation chain-transfer (RAFT) initiator is reported. The use of this novel PEG macroinitiator allows for the controlled polymerization of cationic and thermosensitive linear triblock copolymers and labeling of the chain-end with a fluorescent dye by maleimide–thiol chemistry. The polymers consisted of a thermosensitive poly(N-isopropylacrylamide) (PNIPAM, N), hydrophilic PEG (P), and cationic poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA, D) block, further referred to as NPD. Polymer block D chain-ends were labeled with Cy3, while pDNA was labeled with FITC. The thermosensitive NPD polymers were used to prepare pDNA polyplexes, and the effect of the N/P charge ratio, temperature, and composition of the triblock copolymer on the polyplex properties were investigated, taking nonthermosensitive PD polymers as the control. FRET was observed both at 4 and 37 °C, indicating that the introduction of the thermosensitive PNIPAM block did not compromise the polyplex structure even above the polymer’s cloud point. Furthermore, FRET results showed that the NPD- and PD-based polyplexes have a less dense core compared to polyplexes based on cationic homopolymers (such as PEI) as reported before. The polyplexes showed to have a dynamic character meaning that the polymer chains can exchange between the polyplex core and shell. Mobility of the polymers allow their uniform redistribution within the polyplex and this feature has been reported to be favorable in the context of pDNA release and subsequent improved transfection efficiency, compared to nondynamic formulations.

Synthesis and properties of long-chain-branched poly(aryl ether sulfone)-poly(tetrahydrofuran) multiblock copolymers

Long-chain-branched poly(aryl ether sulfone)-poly(tetrahydrofuran) multiblock copolymers (PES-BPTHF) composed of hard linear and soft branching segments were synthesized from bromo-terminated poly(tetrahydrofuran) and hydroxy-terminated poly(aryl ether sulfone). A study on the effect of concentration on polymerization behavior revealed that soluble powder was obtained at the optimized reaction concentration of 7 wt%. Gelation and intramolecular cyclization were observed at high and low concentrations, respectively. The microphase-separated morphology of PES-BPTHF was confirmed by atomic force microscopy, small-angle X-ray scattering (SAXS), and dynamic mechanical analysis (DMA) measurements. Fewer entangled poly(tetrahydrofuran) segments were detected in PES-BPTHF than in PES-PTHF by SAXS, DMA and tensile measurements. Rheological measurements suggested high chain entanglement of PES-BPTHF in its melt phase. It is interesting to note that the polymer chains in the soft domains become less entangled and more reminiscent of hyperbranched architectures, whereas the overall chain entanglements are increased due to the long-chain-branched structure. Long-chain-branched poly(aryl ether sulfone)-poly(tetrahydrofuran) multiblock copolymers composed of hard linear and soft branching segments were synthesized from bromo-terminated poly(tetrahydrofuran) and hydroxy-terminated poly(aryl ether sulfone). Optimization of the polymerization conditions afforded soluble powder at a reaction concentration of 7 wt%. Microphase-separated morphology was observed for the branched multiblock copolymers. Compared with the corresponding linear multiblock copolymer, the branched polymer chains in the soft domains become less entangled and more reminiscent of hyperbranched architectures, whereas the overall chain entanglements are increased due to the long-chain-branched structure.

Tetraphenylsilane‐Cored Star‐Shaped Amphiphilic Block Copolymers for pH‐Responsive Anticancer Drug Delivery

AbstractFour‐arm star‐shaped poly[2‐(diethylamino)ethyl methacrylate]‐b‐poly[2‐hydroxyethyl methacrylate]s block copolymers using tetraphenylsilane (TPS) as a core with adjustable arm lengths are synthesized through two‐step atom transfer radical polymerizations. For comparison, a linear block copolymer with similar molecular weight is also prepared. The assembled star‐shaped copolymer micelles exhibit sizes of 102–139 nm and critical micelle concentrations of 1.49–3.93 mg L−1. Moreover, the bulky and rigid TPS core is advantageous for propping up the four star‐shaped arms to generate large intersegmental space. As a result, the drug‐loading capacity in the micelles is up to 33.97 wt%, much surpassing the linear counterpart (8.92 wt%) and the previously reported star‐shaped copolymers prepared using pentaerythritol as the core. Furthermore, the micelles show sensitive pH‐responsive drug release when the pH changes from 7.4 to 5.0. The in vitro cytotoxicity to Hela cells indicates that the doxorubicin (DOX)‐loaded micelles have similar anticancer activity to the pristine DOX. The combination of excellent micelle stability, high drug‐loading, sensitive pH response, and good anticancer activity endows the copolymers with promising application in drug control delivery for anticancer therapy.

Comparison of pure and mixed gas permeation of the highly fluorinated polymer of intrinsic microporosity PIM-2 under dry and humid conditions: Experiment and modelling

This manuscript describes the gas separation performance of PIM-2, a partially fluorinated linear copolymer synthesized from 5,5′,6,6′-tetrahydroxy-3,3,3′,3′-tetramethylspirobisindane (TTSBI) and decafluorobiphenyl (DFBP). As one of the early members of the family of polymers of intrinsic microporosity, it had never been tested as a gas separation membrane because of insufficient mechanical resistance. This has been solved only recently, allowing the preparation of robust self-standing films. Molecular modelling studies demonstrated a high fractional free volume (34%) and an elevated surface area (642 m2 g−1), and the latter is in good agreement with experimental BET results. Pure gas permeabilities measured on a fixed-volume time-lag instrument at 1 bar compare well with the results of mixed separation tests on a variable volume setup from 1-6 bar(a). Molecular modelling and independent sorption measurements on a gravimetric sorption balance both show strong dual-mode sorption behaviour, especially for CO2 and to a lesser extent for CH4. Temperature-dependent pure gas permeation measurements show typical Arrhenius behaviour, with a clear increase in the activation energy for diffusion with the increasing molecular size of the gas, indicating high size-selectivity. This is in agreement with the highly rigid PIM structure, determined by AFM force spectroscopy measurements. The dual-mode behaviour results in a moderate pressure dependence of the CO2 permeability and the CO2/N2 and CO2/CH4 selectivity, all slightly decreasing with increasing pressure. The presence of humidity in the gas stream has a remarkable small effect on the membrane performance, which is probably due to the high fluorine content and the consequently low water vapour solubility in the polymer, as confirmed by gravimetric sorption measurements. The manuscript describes an extensive study on the structure-property relationships in PIM-2.

Synthesis of Pentablock Copolymers of the Mixed Linear-Brush Topology by Controlled Radical Polymerization and Ring-Opening Polymerization Reactions

Controlled atom-transfer radical polymerization and ring-opening polymerization methods are used for the first time to synthesize symmetric pentablock copolymers with a central block, which is a polymer brush with the polyimide backbone and poly(methyl methacrylate) side chains, and outer linear block copolymers of poly(e-caprolactone) with poly(methyl methacrylate). The chemical structure of the polymers is studied by 1H NMR spectroscopy. The molecular weight characteristics of the synthesized pentablock copolymers are determined by multidetector size exclusion liquid chromatography. It is shown that these characteristics are in good agreement with the absolute molecular weights obtained by sedimentation-diffusion analysis.

Efficient Aggregation-Induced Emission Manipulated by Polymer Host Materials.

Linear copolymer hosts bearing a number of pillar[5]arene dangling side chains are synthesized for the facile construction of highly emissive supramolecular polymer networks (SPNs) upon noncovalently cross-linking with a series of tetraphenyethylene (TPE)-based tetratopic guests terminated with different functional groups through supramolecular host-guest interactions. An extremely high fluorescence quantum yield (98.22%) of the SPNs materials is obtained in tetrahydrofuran (THF) by fine-tuning the parameters, and meanwhile supramolecular light-harvesting systems based on spherical supramolecular nanoparticles are constructed by interweaving 9,10-distyrylanthracene (DSA) and TPE-based guest molecules of aggregation-induced emission (AIE) with the copolymer hosts in the mixed solvent of THF/H2 O. The present study not only illustrates the restriction of the intramolecular rotations (RIR)-ruled emission enhancement mechanism regulated particularly by macrocyclic arene-containing copolymer hosts, but also suggests a new self-assembly approach to construct high-performance light-harvesting materials.

Synthesis of novel (bio) degradable linear azo polymers conjugated with olsalazine

Click Cu(I)-catalyzed polymerization of diynes and diazides was performed to obtain a novel type of linear copolymer, which were prepared from monomers derived from poly(ethylene glycol), 5, 5′-azodisalicylic acid [olsalazine] and 1,4-butanediol diglycidyl ether. The resulting copolymers will carry ester and azo functions along the polymer backbone, so they will be sensitive to pH as well as be degraded by azoreductase enzymes present in the colonic microbiota. Most of the copoly(azoester triazole)s obtained were water soluble, and all of them were characterized by Fourier transform infrared, nuclear magnetic resonance (NMR), and gel permeation chromatography (GPC). Differential scanning calorimetry (DSC) revealed them to be amorphous, and in general, the polymers were stable up to 250 °C under nitrogen as demonstrated by thermogravimetric analysis (TGA). The degradation behavior of the polymers was evaluated in vitro. Degradation studies were carried out at 37 °C in buffered salt solution at pH 7.4, and were monitored by GPC and NMR spectroscopies. A biodegradation experiment of a water-soluble prototype polymer showed that they are biodegradable via a strain of Enterococcus faecalis. The experiment was monitored using ultraviolet–visible spectroscopy.

Nonionic Amphiphilic Linear Dendritic Block Copolymers. Solvent-Induced Self-Assembly and Morphology Tuning

In this article, we report the solution self-assembly of a series of amphiphilic linear–dendritic block copolymers (LDBCs), which are composed of hydrophilic dendritic poly(ether-ester), PEE, blocks based on 2,2-bis(hydroxymethyl)propionic acid and hydrophobic linear poly(styrene), PSt, blocks. The investigated LDBCs have narrow dispersity with three PEE generations (1–3) and a broad range of PSt molecular masses and are produced by dendron-initiated atom transfer radical polymerization of styrene followed by deprotection of the peripheral dendron hydroxyl groups. The solution self-assembly of the copolymers is performed by slowly adding water to the polymer solution in tetrahydrofuran (THF) as the common solvent for both blocks of the copolymers. The morphologies of the supramolecular assemblies are preserved either by diluting their dispersion by excess of water or by THF evaporation. It is found that the micellar morphology (sphere, wormlike, and/or vesicle) depends on the hydrophilic block fraction (F...

Investigating Molecular Exchange between Partially Cross-Linked Polymer Particles Prepared by a Secondary Dispersion Process

We recently described a new approach to surfactant-free latex dispersions prepared by emulsification of a partially neutralized linear acrylic acid-containing styrene-acrylic copolymer without the ...

Effects of comb-like PCE and linear copolymers on workability and early hydration of a calcium sulfoaluminate belite cement

Fluidity control and setting adjustment are two critical issues for practical applications of calcium sulfoaluminate cement because of rapid hydration. A commonly used comb-like polycarboxylate superplasticizer (PCE) and linear copolymers (PAS) of acrylic acid (AA) and 2-acrylamido-2-methylpropane sulfonic acid (AMPS) with varied monomer ratio were synthesized to study their impacts on fluidity and early hydration of calcium sulfoaluminate belite cement (CSAB). Results show that the linear PAS polymers are very effective in dispersing fresh cement pastes (fcps) and effectively inhibit early hydration of the cement. More AA unit in the PAS molecules leads to stronger inhibition effect on cement hydration. Compared with the PAS polymers, PCE exhibits almost no inhibition effect on cement hydration despite the high initial dispersibility. Thus, cement pastes containing PAS polymers exhibits excellent fluidity retention compared with the PCE containing fcp due to strong retardation effect of the PAS polymers on early formation of AFt crystals.

Electrical, thermal behaviors and synthesis of intramolecular cobalt phthalocyanine with single-chain polymer structure

Firstly, poly[4-(4-vinylbenzyl)oxy)phthalonitrile]-co-styrene, [poly(VBOP-co-St], which is used as a linear copolymer precursor containing phthalonitrile pendant group was prepared from copolymerization of VBOP and St by atom transfer radical polymerization method at 110 °C. Then, complex synthesis of cobalt phthalocyanine in the single-chain polymer (SCP-CoPc complex) via the intramolecular macrocyclization reaction of cobalt and phthalonitrile group in poly(VBOP-co-St) was carried out at 150 °C in the presence of excess cyclohexanol. Both linear copolymer precursor and formation of cobalt phthalocyanine within a single-chain polymer were confirmed by FT-IR, 1H-NMR, 13C-NMR and UV/Vis spectroscopy techniques. Particularly, the formation of SCP-CoPc complex was characterized by almost disappearance of –C≡N band at 2230 cm−1 of the FT-IR and appearance of Q band around 672 nm and the B band in the near UV region at 350 nm of UV/Vis spectroscopy. The pure poly(VBOP-co-St), SCP-CoPc complex and the residue SCP-CoPc complex heated to 500 °C were characterized by SEM images, and the element analyses were estimated from X-ray energy dispersive spectroscopy (X-ray EDS). The EDS elemental analysis results of the residual of SCP-CoPc complex degraded to 500 °C showed that CoO [cobalt(II)oxide] compound occurred. The thermal properties of poly(VBOP-co-St) and SCP-CoPc complex were investigated through thermogravimetric analysis and differential scanning calorimeter. The conducting nanographene-based SCP-CoPc composites were prepared. DC and AC electrical conductivity and dielectric properties were investigated. The ac dielectric measurements of poly(VBOP-co-St), SCP-CoPc complex and composites were investigated at room temperature between 100 and 20 kHz depending on the alternating current conductivities. Also, the activation energy profile of SCP-CoPc/4% (by wt) nanographene composite was revealed by measuring the DC conductivity of individual composite material.

Metal– and Covalent Organic Frameworks Threaded with Chiral Polymers for Heterogeneous Asymmetric Catalysis

Porous metal–organic frameworks (MOFs) and covalent organic frameworks (COFs) were composited with homogeneous linear chiral copolymers threaded within the host cavity of MOFs/COFs, demonstrating a...

Identification of Some New Triply Periodic Mesophases from Molten Block Copolymers.

Using field-theoretic simulations based on a self-consistent field theory (SCFT) with or without finite compressibility, nanoscale mesophase formation in molten linear AB and ABC block copolymers is investigated in search of candidates for new and useful nanomaterials. At selected compositions and segregation strengths, the copolymers are shown to evolve into some new nanostructures with either unusual crystal symmetry or a peculiar morphology. There exists a holey layered morphology with Im3 symmetry, which lacks one mirror reflection compared with Im3m symmetry. Also, a peculiar cubic bicontinuous morphology, whose channels are connected with tetrapod units, is found to have Pn3m symmetry. It is shown that there is another network morphology with tripod connections, which reveals P432 symmetry. The optimized free energies of these new mesophases and their relative stability are discussed in comparison with those of double gyroids and double diamonds.

Self-assembly of tunable ABC miktoarm terpolymers with semi-fluorinated segment for the discovery of a rich diversity of multicompartment micelles

A series of highly ordered morphologies in aqueous solution were obtained by self-assembly of ABC miktoarm terpolymers with mutually immiscible hydrophilic poly(ethylene glycol) monomethyl ether (mPEG), hydrophobic polystyrene (PS) and superhydrophobic poly(1H,1H,5H-octafluoropentyl methacrylate) (POFPMA), which were synthesised by a combination of atom transfer radical polymerisation (ATRP), single electron transfer living radical polymerisation (SET-LRP) and click chemistry. Perforated stomatocytes, raspberry-like micelles, and segmented worm-like micelles, difficult to obtain from linear triblock copolymers, were readily prepared from terpolymers mPEG-arm-POFPMA-arm-PS (denoted μ-EFS). Compartmentalization behaviours of the assemblies were investigated by fixing the length of mPEG but adjusting the ratio of hydrophobic and superhydrophobic segments of the terpolymers μ-EFS, which allows us to establish the correlation between self-assembled morphology and the composition of the terpolymers. The abundant morphological transformation of μ-EFS indicates this type of polymer can serve as a reliable platform for discovery of new self-assembled morphologies with highly ordered superstructures.