Acrylate Block Copolymers Research Articles

Mechanical and Thermal Properties of Polypropylene, Polyoxymethylene and Poly (Methyl Methacrylate) Modified with Adhesive Resins

Polyoxymethylene (POM), polypropylene (PP), and poly(methyl methacrylate) (PMMA) have been blended with adhesive-grade ethylene vinyl acetate (EVA), propylene elastomer (VMX), isobutylene–isoprene rubber (IIR) and an acrylic block copolymer (MMA-nBA-MMA). The blends were prepared using a two-roll mill and injection molding. The mechanical properties of the blends, such as tensile strength, tensile modulus, elongation at maximum load, and impact resistance, were investigated. The water contact angle, melt flow rate (MFR), and differential scanning calorimetry were ascertained to evaluate the blends. The blend samples exhibited the following properties: all POM/EVA blends showed reduced crystallinity compared to neat POM; the 80% PMMA/20% MMA-nBA-MMA blend showed improved impact resistance by 243% compared to the neat PMMA. An antiplasticization effect was observed for POM/EVA 1% blends and PMMA/EVA 1% blends, with MFR reduced by 1% and 3%, respectively. The MFR of the PP/IIR 1% blend increased by 5%, then decreased below the MFR near the polymer for the remaining IIR concentrations.

2-Cyanopropan-2-yl versus 1-Cyanocyclohex-1-yl Leaving Group: Comparing Reactivities of Symmetrical Trithiocarbonates in RAFT Polymerization.

This study introduces bis(1-cyanocyclohex-1-yl)trithiocarbonate (TTC-bCCH) as a novel trithiocarbonate chain transfer agent and compares its reactivity with the previously described bis(2-cyanopropan-2-yl)trithiocarbonate (TTC-bCP) for the reversible addition-fragmentation chain transfer (RAFT) polymerization of styrene (St), n-butyl acrylate (nBA), and methyl methacrylate (MMA). Significant findings include the effective control of Mn and low dispersities from the onset of polymerization of St and nBA showing swift addition-fragmentation kinetics, leading to similar behaviors between the two RAFT agents. In contrast, a fourfold decrease of the chain transfer constant to MMA is established for TTC-bCCH over TTC-bCP. This trend is confirmed through density functional theory (DFT) calculations. Finally, the study compares thermoplastic elastomer properties of all-(meth)acrylic ABA block copolymers produced with both RAFT agents. The impact of dispersity of PMMA blocks on thermomechanical properties evaluated via rheological analysis reveals a more pronounced temperature dependence of the storage modulus (G') for the triblock copolymer synthesized with TTC-bCCH, indicating potential alteration of the phase separation.

Microphase separation of double-hydrophilic poly(carboxybetaine acrylate)-poly(2-methoxyethyl acrylate) block copolymers in water

Microphase separation of double-hydrophilic poly(carboxybetaine acrylate)-poly(2-methoxyethyl acrylate) block copolymers in water

Synthesis of soft-core hard-shell nanoparticles by visible PET-RAFT polymerization in dispersion conditions

Photoinduced electron/energy transfer (PET)-RAFT polymerization is an innovative technique for the synthesis of new nanomaterials moving towards greener conditions and process optimization. In the current work, we present a fast, simple, and robust methodology for the synthesis of spherical soft-core hard-shell nanoparticles in a fashionable controlled way. We exploited ZnTPP for the synthesis of poly(dimethyl acrylamide)-b-poly(butyl acrylate) (PDMA-b-PBA) block copolymer in various alcoholic media in dispersion conditions. The use of a homemade photoreactor allows to carry out several reactions simultaneously and to obtain quickly the optimization of the experimental conditions. In all cases, NMR analysis highlights the success of the PDMA-b-PBA polymerizations with very good yield (α > 75%) and low dispersity (Đ < 1.3). Dynamic light scattering (DLS) and TEM microscopy were used to analyze the NPs morphology, which varies from spherical-like shape to more complex second-order structures, depending on the water content of the alcoholic media. In order to improve the particles synthesis, making the process easier to scale up and reducing the use of organic solvents, one-pot polymerization was implemented with promising results. Finally, we demonstrate that a significant amount of photocatalyst is retained in the soft core, feature that can open the door for the production of innovative materials for photophysic applications.

Topology-controlled self-assembly of amphiphilic block copolymers.

Contemporary synthetic chemistry approaches can be used to yield a range of distinct polymer topologies with precise control. The topology of a polymer strongly influences its self-assembly into complex nanostructures however a clear mechanistic understanding of the relationship between polymer topology and self-assembly has not yet been developed. In this work, we use atomistic molecular dynamics simulations to provide a nanoscale picture of the self-assembly of three poly(ethylene oxide)-poly(methyl acrylate) block copolymers with different topologies into micelles. We find that the topology affects the ability of the micelle to form a compact hydrophobic core, which directly affects its stability. Also, we apply unsupervised machine learning techniques to show that the topology of a polymer affects its ability to take a conformation in response to the local environment within the micelles. This work provides foundations for the rational design of polymer nanostructures based on their underlying topology.

Temperature-triggered fluorocopolymer aggregate coating switching from antibacterial to antifouling and superhydrophobic hemostasis

The multifunction antibacterial hemostatic materials can reduce blood loss, infection and wound complications, which probably decrease morbidity and health care costs. However, the contradictory relationship between antibacterial ability and biocompatibility, and the unnecessary blood loss restricts the practical application of hydrophilic cationic antibacterial hemostatic materials. Herein, a multifunctional temperature-triggered antibacterial hemostatic fluorocopolymer aggregate coating was developed. After self-assembly and quaternization process, the quaternized poly(N,N-dimethylaminoethylmethacrylate)-b-poly(1H,1H,2H,2H-heptadecafluorodecyl acrylate) block copolymers (PDMA-b-PFOEMA) aggregate coating consisting of fluoropolymer and quaternary ammonium salt were built. The synergistic effect on fluorinated block with low surface energy and quaternary ammonium salt block with bactericide activity severs the way of initial bacterial attachment and proliferation, while the migration of fluorinated block greatly promotes the biocompatibility and anti-adhesion performance in response to the switch from room temperature to physiological temperature. Furthermore, the fluorocopolymer aggregate coating with hydrophobic properties possessed the property of rapid coagulation, low blood loss, minor secondary bleeding and least bacteria infiltration. The multifunctional temperature-triggered fluorocopolymer aggregate coating with antifouling, antibacterial and hemostatic properties may have a great potential in the biomedical application.

Maltotriose-based star polymers as self-healing materials

Self-healing polymers with complementary functional groups can spontaneously repair mechanical damage. We developed star-like block copolymers from a naturally-derived maltotriose core with acrylate arms consisting of soft poly(n-butyl acrylate) (PnBA) and hard poly(tert-butyl acrylate) (PtBA) segments, exhibiting self-repair behavior. A facile and efficient two-step synthesis involving a “core-first” approach employed a simplified electrochemically mediated ATRP (seATRP) with only 25 ppm of a copper catalyst. Precise control was maintained during the polymerization of both acrylates, yielding soft and hard segments. Macromolecules with maltotriose core and polymer arms composed of PnBA homopolymer or poly(n-butyl acrylate)-block-poly(tert-butyl acrylate) (PnBA-b-PtBA) block copolymer had a narrow molecular weight distribution (Mw/Mn = 1.13 and 1.17, respectively). Thermomechanical properties of maltotriose-based star-like copolymers and their linear counterpart were studied by thermogravimetry (TGA), differential scanning calorimetry (DCS) and tensile analysis. The star-like polymers exhibited self-healing behavior. A complete repair of the damaged material occurred after 30 min without external intervention under ambient conditions.

Thermoresponsive chimeric nanocarriers as drug delivery systems

Chimeric or mixed nanosystems belong to the class of advanced therapeutics. Their distinctive characteristic compared with other types of nanoparticles is that they combine two or more different classes of biomaterials. These platforms have created a promising and versatile field of nanomedicine, incorporating materials that are biocompatible, such as lipids, but also functional, such as stimuli-responsive polymers. In the present work, thermoresponsive chimeric nanocarriers composed of l-α-phosphatidylcholine (Egg, Chicken) (EPC) phospholipids and poly(N-isopropylacrylamide)-b-poly(lauryl acrylate) (PNIPAM-b-PLA) block copolymers were designed and developed. Initially, model lipid bilayers with incorporated polymers and drug molecule TRAM-34 were built and studied for their thermodynamics, in order to assess the stability and functionality of the systems. Chimeric nanoparticles of EPC and PNIPAM-b-PLA were then developed and evaluated for their physicochemical properties in different medium conditions, as well as for their morphology. Polymer incorporation led to alterations in the properties and morphology of the nanoparticles, while interactions with serum proteins were absent. TRAM-34 was also incorporated inside the developed nanocarriers, followed by incorporation and release studies, which revealed the functionality of the system in elevated temperature conditions. Finally, in vitro studies on normal cells suggest the biocompatibility of these nanosystems. The proposed platforms are promising for further studies and applications in vitro and in vivo.

Phase structure and adhesion properties of acrylic block copolymer/tackifier blends as nanocomposite‐like pressure‐sensitive adhesives

AbstractIn a blend of acrylic block copolymer consisting of poly(methyl methacrylate) and poly(n‐butyl acrylate) blocks and a special rosin ester resin (RE) tackifier as a model pressure‐sensitive adhesive (PSA), RE exists in two states: as nm‐sized agglomerated particles (A) and as dissolved molecules (B). The effect of A and B ratio on the PSA properties were investigated using REs with four different weight‐average molecular weights (Mws) in the range from 680 to 1700. The formation of A increased with increasing of Mw because of lowering of miscibility. The glass transition temperature increased with increasing of Mw. The tack at lower temperatures and the fracture energy were improved by B, whereas the tack at higher temperatures was improved by A. A and B enhanced the cohesive strength and the wettability of PSA, respectively. However, the improvement of cohesive strength by the RE with highest Mw was remarkably low. This seems to be caused by the larger size of agglomerated particles. 1H pulse nuclear magnetic resonance analysis was useful for estimating the degree of A formation. The model PSA investigated in this study was nanocomposite‐like.

Nano-cavitation structure toughness mechanism and optical properties of amphiphilic acrylate block copolymer modified epoxy system

A series of amphiphilic acrylate block copolymer (ABC) modified epoxy were prepared by the solution casting method. The mechanical strength, thermal stability, and light transmittance of the modified epoxies were characterized, and the fracture surfaces of the ABC modified epoxy were characterized with multi techniques for the toughening mechanism exploration. The results indicated that the glass transition temperature (Tg) and tensile strength of the ABC modified epoxy would be slight increased as 10 phr ABC was incorporated into epoxy matrix compared with neat epoxy. Surprisingly, the critical strain energy release rate (GIC) and plan strain fracture toughness (KIC) of the blend with 10 phr ABC/epoxy were 8 times and 2 times higher than that of the neat epoxy at room temperature, respectively. When the addition amount of ABC reached up to 30 phr, the ABC modified epoxy showed superior adhesion strength and still remained excellent optical property. The nano-cavitation of rubbery core which facilitated shear yielding of the epoxy matrix was found to be the main toughening mechanism. Both theoretical and experimental results strongly indicate that ABC modified epoxy is a new type of composite material with excellent mechanical properties and light transmittance.

Synthesis of well-defined di- and triblock acrylic copolymers consisting of hard poly(dicyclopentanyl acrylate) and soft poly(alkyl acrylate) segments by organocatalyzed group transfer polymerization and their glass transition behavior

Well-defined acrylic block copolymers with hard poly(dicyclopentanyl acrylate) and soft poly(n-alkylacrylate) blocks prepared by GTP are observed to undergo microphase separation by rheometry except for the crystallizable poly(n-dodecyl acrylate) series.

Synthesis, Characterization and Self-Assembly Properties of a New Copper-Phthalocyanine Core Acrylate Block Copolymer

A new di-block acrylate copolymer with a Copper-Phthalocyanine (CuPc) core has been synthesized via a multi-step reaction scheme involving the atom-transfer radical polymerization. This material displayed amphiphilic character and consists of a CuPc core with eight copolymer arms. This new amphiphilic material and related intermediates have been characterized by UV-Vis, FT-IR, 1H-NMR and elemental analysis. A preliminary study involving self-assembly properties of this material by optical, atomic force and scanning electron microscopies is presented.

Pyrolysis gas chromatography – mass spectrometry of pressure sensitive adhesive tapes

Conservators and restorers often encounter pressure sensitive adhesive tapes used for conservation reasons. This type of tape has been used to repair documents or pages of books or on torn documents. The adhesives frequently found are composed of either natural or synthetic rubber or of acrylics. The pressure sensitive adhesive tapes (PSTs) consist of four layers: the release coating, the backing, the primer and the adhesive.The restoration often requires the removal of the adhesive or backing or any other of the PST layers affecting paper artworks since degradation products could originate from one or more of these layers. In this work, six pressure sensitive adhesive tapes often found on paper works of art were analysed with Py-GC–MS in order to obtain a chemical classification of the PSTs as a whole, as well as, for the first time, of the single layers. The pyrolytic products detected allowed to recognize two main classes of adhesives: acrylic and styrene block copolymers. Among acrylic types, different copolymers, such as poly(n-butyl acrylate - methyl methacrylate - 2-ethylhexyl acrylate), poly(n-butyl acrylate - methyl methacrylate) and poly(n-butyl acrylate - ethyl acrylate) have been used often together with phthalate and adipate plasticizers. On the other hand, the styrene-isoprene-styrene and the styrene-butadiene-styrene copolymers were identified for styrene block type. In these adhesives, more terpenoid tackifiers have been revealed. In the backing layers the pyrolyzates suggested the use of polypropylene, cellulose acetate, paper or polyvinyl chloride. Only for one sample, the insulating tape, it was possible to detach the release coating from the backing layer and so to identify its acrylic nature. The exact knowledge of different layers of PSTs could help restorers to select an optimal removal procedure.

Synthesis of β-cyclodextrin derivatives and their selective separation behaviors for U(VI) in solution

In this study, four functional β-cyclodextrin derivatives including amidoxime linear-linked and cross-linked β-cyclodextrin/acrylonitrile/acrylic terpolymer (l-CD-AO-AA and c-CD-AO-AA), citric acid cross-linked poly-β-cyclodextrin (PCD), amidoxime cross-linked β-cyclodextrin and acrylonitrile–acrylic block copolymer (CD-b-AO-AA) were synthesized and properties of β-CD derivatives were characterized by FT-IR, SEM, TGA and element analysis. The effect of solid liquid ratio of the adsorbents, ionic strength, pH, contact time, initial concentration of U(VI), adsorption temperature, selective adsorption for different metal ions and the reasonable desorption conditions were studied. It was found when content of U(VI) was 22 mg/L, the four functional materials l-CD-AO-AA, c-CD-AO-AA, PCD and CD-AO-b-AA completely adsorbed U(VI) at 0.06 g/L (R ≈ 97%), 0.10 g/L (R ≈ 96%), 0.08 g/L (R ≈ 94%) and 0.52 g/L (R ≈ 94%), respectively.

Effect of Technogenic Factors and Biodestructive Agents on the Thermal Behavior of Chitosan and Poly(methyl acrylate) Block Copolymer

Thermal analysis of samples of chitosan–poly(methyl acrylate) block copolymer after exposure to electromagnetic fields, ultraviolet radiation, ultrasound, and biodestructive agents is performed for the first time by means of differential scanning calorimetry in the range of 250–510 K and thermogravimetry in the region of 300–850 K. It is shown that the combined effect of physical factors and biodestructive agents alters certain physicochemical properties: the temperatures of physical transformations, the temperatures of the onset of thermal degradation, and the nature of thermal decomposition.

Synthesis of 4-acetoxystyrene – t-butyl acrylate statistical, block and gradient copolymers, and the effect of the structure of copolymers on their properties

The properties of copolymers are affected greatly by the composition as well as the chain structure of the copolymers. Consequently, gradient copolymers, due to the uniqueness of their structures show significantly different properties than those of the conventional statistical and block copolymers. This study reports the synthesis of 4-acetoxystyrene – t-butyl acrylate (AOST-tBA) statistical copolymers by reversible addition-fragmentation chain-transfer (RAFT) and free radical polymerization (FRP) methods, and also the synthesis of block and gradient copolymers of AOST-tBA by the RAFT method. The gradient structure in the AOST-tBA copolymer was produced by continuously adding a second monomer to the polymerization system to taper the copolymer composition. Differential scanning calorimetry (DSC) analysis found a broad transition for the gradient copolymer, in contrast to a single narrow transition for the statistical copolymer and two narrow transitions for the block copolymer. The acetoxy groups from the AOST-tBA copolymers were de-acetylated to convert the AOST to hydroxystyrene (HOST). Fourier transform infra-red (FTIR) studies revealed that the extent of hydrogen bonding in thin films of the HOST-tBA copolymers is greatly influenced by the copolymer composition as well as the chain structure. However, no significant differences were found for the surface compositions and surface free energies of copolymers. The properties of HOST-tBA copolymers synthesized by RAFT and FRP have also been compared in this study.

Design and synthesis of fluorescent shell functionalized polymer micelles for biomedical application

pH‐sensitive polymers can be defined as polyelectrolytes that include in their structure weak acidic or basic groups that either accept or release protons in response to a change in the environmental pH. This work summarizes the design, synthesis, and potential applications of pH‐responsive fluorescent copolymers in the biomedical field. This was achieved using atom transfer radical polymerization (ATRP) of tert‐butyl acrylate using a CuBr/N,N,N′,N″N″‐pentamethyldiethylenetriamine catalyst system in conjunction with an alkyl bromide as the initiator. Well‐defined macroinitiators based on poly(tert‐butyl acrylate) with narrow molecular weight distributions were obtained by the addition of an appropriate solvent system in order to create a homogeneous catalytic system. The addition of n‐butyl acrylate as a second building block in order to create well‐defined poly(tert‐butyl acrylate)‐b‐poly(n‐butyl acrylate) block copolymers (PtBA‐b‐PnBA) followed by chemical modification of the block copolymers and functionalization with an appropriate fluorescent compound are the basis for the preparation of well‐defined fluorescent pH‐sensitive micelles. Thus, prepared water soluble nanosized pH‐sensitive micelles consisting of hydrophobic poly(n‐butyl acrylate) core and hydrophilic polyacrylic acid shell decorated with an appropriate fluorescent compound determined their potential applications of these systems in the field of biomedicine as biosensors, controlled drug delivery systems, and so on. In this respect, the cell viability and internalization of the polymer micelles were studied.

Microwave Processing Controls the Morphology of Block Copolymer-Templated Mesoporous Cobalt Oxide Films.

Microwave heating provides an efficient method to rapidly heat materials through interaction of microwaves with the media. Here, we demonstrate the rapid synthesis of mesoporous cobalt oxide films through the heating of the silicon substrate by microwaves. A non-sol-gel approach based on cobalt nitrate-citric acid complex cooperative assembly with a poly[methoxy poly(ethylene glycol)methacrylate]-block-poly(butyl acrylate) (PMPEGMA-b-PBA) block copolymer was used to fabricate the cobalt oxide through a cobalt carbonate intermediate. The time required to convert cobalt carbonate to cobalt oxide with the full removal of the PMPEGMA-b-PBA template can be decreased by two orders of magnitude with microwaves in comparison to standard heating in a furnace at 350 °C. At the highest microwave power examined (1500 W), this can be accomplished within 2 s, while >5 min is required at 350 °C in a furnace. At a microwave power of <400 W, there is insufficient energy to induce the transition from carbonate to oxide, but even at only 420 W, the oxide can be formed within 26 s. The rapid heating by the microwaves tends to increase the crystallinity and mean crystal size of the cobalt oxide within the mesoporous films. Despite the growth of larger average crystals, the pore size and porosity tend to be larger when the film is processed using microwaves. Higher microwave power leads to larger average crystals and average pore size. These results suggest that rapid processing to crystallize frameworks in mesoporous materials may allow for highly crystalline frameworks without loss of the templated mesostructure.

Preparation of Nitrogen-Doped Mesoporous Carbon for the Efficient Removal of Bilirubin in Hemoperfusion.

The development of bilirubin adsorbent with high selectivity, brilliant adsorption ability, and biocompatibility is still a considerable challenge. In this study, a copolymer-templated nitrogen-doped mesoporous carbon (CTNC) has been prepared via a simple carbonization procedure of well-defined polyacrylonitrile-block-poly(n-butyl acrylate) (PAN-b-PBA) block copolymer precursors. The structure and morphology were characterized by transmission electron microsphere (TEM), adsorption-desorption isotherms, and X-ray photoelectron spectroscopy (XPS). Owing to its high specific area, hierarchical open-porous structure, and the introduction of nitrogen atoms in graphitic sp2 network, the adsorbent CTNC exhibited high removal efficiency toward bilirubin and bile acid from human plasma. The removal rate of bilirubin was more than 50.7% with a minimal loss of albumin. Meanwhile, exceeding 95% of bile acid was eliminated. The effect of albumin on the adsorption kinetic of bilirubin was identified. The result indicated that the adsorption rate of BSA-bonded bilirubin experienced a decline than that of free bilirubin, but the adsorption capacity was still up to 39.8 mg/g within 2 h. Moreover, the effect of porosity and nitrogen contents on bilirubin adsorption ability and blood compatibility were systematically investigated. The material with lower nitrogen content showed only a negligible hemolysis activity. Therefore, the nitrogen-doped mesoporous carbon developed in this work has potential application in blood purification for the efficient removal of bilirubin.

Tellurium-Doped, Mesoporous Carbon Nanomaterials as Transparent Metal-Free Counter Electrodes for High-Performance Bifacial Dye-Sensitized Solar Cells.

Tellurium-doped, mesoporous carbon nanomaterials with a relatively high doping level were prepared by a simple stabilization and carbonization method in the presence of a tellurium metalloid. A transparent counter electrode (CE) was prepared using tellurium-doped, mesoporous carbon (TeMC) materials, and was directly applied to bifacial, dye-sensitized solar cells (DSSCs). To improve the performance of the bifacial DSSC device, CEs should have outstanding electrocatalytic activity, electrical conductivity, and electrochemical stability, as well as high transparency. In this study, to make transparent electrodes with outstanding electrocatalytic activity and electrical conductivity, various TeMC materials with different carbonization temperatures were prepared by simple pyrolysis of the polyacrylonitrile-block-poly (n-butyl acrylate) (PAN-b-PBA) block copolymer in the presence of the tellurium metalloid. The electrocatalytic activity of the prepared TeMC materials were evaluated through a dummy cell test, and the material with the best catalytic ability was selected and optimized for application in bifacial DSSC devices by controlling the film thickness of the CE. As a result, the bifacial DSSC devices with the TeMC CE exhibited high power conversion efficiencies (PCE), i.e., 9.43% and 8.06% under front and rear side irradiation, respectively, which are the highest values reported for bifacial DSSCs to date. Based on these results, newly-developed transparent, carbon-based electrodes may lead to more stable and effective bifacial DSSC development without sacrificing the photovoltaic performance of the DSSC device.