ABA Triblock Copolymers Research Articles

Gas-separation and physical properties of ABA triblock copolymers synthesized from polyimide and hydrophilic adamantane derivatives

In this study, ABA triblock copolymers derived from 4,4’-(hexafluoroisopropylidene)-diphthalic anhydride-2,3,5,6-tetramethyl-1,4-phenylenediamine (6FDA-TeMPD; PI) and 3-hydroxy-1-adamantyl methacrylate (HAdMA) or 3,5-dihydroxy-1-adamantyl methacrylate (DHAdMA) have been synthesized via atom transfer radical polymerization to generate mechanically tough and thermally stable gas-separation membranes with composition-tunable transport properties. Due to the inherent thermodynamic incompatibility between the chemically dissimilar blocks, these two series of triblock copolymers appear microphase-separated. While the gas permeability coefficients of these triblock copolymer membranes are consistently lower than that of PI due to the reduced fractional free volume of HAdMA and DHAdMA, the solubility coefficients of the copolymers are higher than that of PI due presumably to specific interactions between the polar hydroxyl group(s) and penetrant gas molecules. These triblock copolymers synthesized from PI and hydrophilic adamantane derivatives constitute a new class of nanostructured polymeric materials possessing excellent thermomechanical properties in conjunction with designer gas-separation properties.

Synthesis, self-assembly of perfluoropolyether based ABA-triblock copolymers for superhydrophobic surface applications

A series of poly (isobornyl methacrylate)–perfluoropolyether–poly (isobornyl methacrylate) (PIBOMA–PFPE–PIBOMA) triblock copolymers with a fixed PFPE block length and different PIBOMA block lengths are synthesized via atom transfer radical polymerization from a PFPE macroinitiator. The triblock copolymers can self-assemble into micelles with the PIBOMA core and PFPE corona in mixed 1,1,2-trichlorotrifluoroethane/N,N-dimethylformamide (F113/DMF) solvent. Hydrophobic surface can be obtained by evaporating the solvent in the prepared micelles at 23 °C. The surface hydrophobicity of films constructing from the prepared triblock copolymer micelles is successfully regulated by tuning the assembly morphologies through changing the volume ratio of F113/DMF and the chain length of PIBOMA blocks. In the films casting from the micelles at F113/DMF 1/1 (v/v) solvents, the micro-/nano-scale particle structures are coexisted on the surface, which leads to the formation of superhydrophobic surfaces with water contact angle (WCA) of 155° and sliding angle of 4°, as well as good self-cleaning performance. Meanwhile, the self-assembled surfaces show excellent superhydrophobic properties with a WCA of 155° and good corrosion resistance on cotton fabrics. These phenomena indicate that the PFPE-containing triblock copolymers have potential application prospects in superhydrophobic coatings.

Block Copolymer Pressure-Sensitive Adhesives Derived from Fatty Acids and Triacetic Acid Lactone

A method for the development of ABA triblock copolymers for high-performance pressure-sensitive adhesives from the biorenewable chemicals lauryl acrylate and triacetic acid lactone (TAL) is present...

ABA triblock copolyesters composed of poly(l-lactide) A hard blocks: comparison of amorphous and crystalline unsaturated aliphatic polyesters as B soft blocks

The property profiles of ABA triblock copolymers can be precisely customized by changing the chemical structure of the components. The identification of the midblock is the key point in the development of PLLA-containing ABA triblock copolymers. Two kinds of unsaturated aliphatic polyesters, crystalline poly(cis-butene succinate) (PcBS) and amorphous poly(cis-butene glutarate) (PcBG) with dihydroxyl end groups were prepared by polycondensation reactions. Then, dihydroxyl-terminated PcBS and PcBG were used as macroinitiators to initiate ring opening of polymerization of L-lactide toward two series of fully biobased biodegradable PLLA-b-PcBS-b-PLLA and PLLA-b-PcBG-b-PLLA triblock copolymers with PLLA as hard end-blocks. The influences of the midblocks and the endblocks length on microstructure, thermal and tensile properties of the triblock copolymers were studied. Compared to homopolymer PLLA, all the triblock copolymers had a much higher elongation at break with lower tensile strength and tensile modulus, depending on the length of PLLA blocks. It was found that the amorphous PcBG midblock plays a greater role than the crystalline PcBS midblock in enhancing the tensile toughness of ABA triblock copolymers. PLLA-b-PcBG-b-PLLA composed of shorter PLLA hard block displayed typical elastomeric behavior without yield, which is a promising aliphatic polyester-based thermoplastic elastomer. The unsaturated carbon–carbon double bonds in these polyesters backbone provide a variety of opportunities for further modifications.

Quick and Efficient Thermal Stability Enhancement of Micro‐Phase Separated Structure Formed from ABA Triblock Copolymers by Photo Cross‐Linking Approach

AbstractWe here report quick and efficient enhancement of the thermal stability of triblock copolymer‐based bulk morphologies by utilizing photo cross‐linking, which aims for widening the application range of block copolymer‐based materials. First, we synthesized ABA triblock copolymer bearing photo cross‐linkable groups (i. e., benzophenone groups) in the end blocks via two step atom transfer radical polymerizations (ATRP) and subsequent esterification reaction. UV‐light was irradiated for the annealed bulk films at room temperature, and the photo cross‐linking completely progressed within several minutes. Small angle X‐ray scattering (SAXS) and the model fitting analysis revealed that the original cylinder morphology of the neat sample was nicely preserved after the photo cross‐linking, which enables investigation of intrinsic effects of domain cross‐linking. The temperature ramp SAXS measurements demonstrated the photo cross‐linked cylinder structure remained up to the temperature (∼320 °C) much higher than the disordering temperature (∼240 °C) of the neat uncross‐linked structure.

Extraction of intrinsic cross-linking effects of A hard domains on segmental motion of B soft block for ABA triblock copolymer-based elastomers by utilizing photo cross-linking

We here shed light on effects of the A domain cross-linking for the physical properties, especially for the B middle block segmental motion, of ABA triblock copolymers with a soft B block and A glassy end blocks bearing photo cross-linkable moieties. For extraction of the intrinsic effects of cross-linking, we utilize room temperature photo cross-linking. Scattering measurements and model analysis finely confirm that the photo cross-linking proceeds without any influences on the morphology. Unexpectedly, the cross-linking of A domain affects not only the segmental motion of A block but also the B block segmental motion. Concretely, DSC and rheological measurements revealed that Tg (or α-relaxation temperature) of the B soft block decreased (ΔTg ~ 4 °C) and the apparent activation energy (Ea) of the B soft segmental motion increased (ΔEa ~90 kJ mol−1), which were discussed with assuming the rigidity change of B segment in the interfacial mixed layer.

Controlling the thermomechanical properties of biobased ABA triblock copolymers comprising polylactide (A) and poly(1,2‐propylene succinate) (B) with high molecular weight

AbstractBis‐hydroxyl‐terminated poly(1,2‐propylene succinate) (PPS‐diols) with high molecular weight (10–40 kDa) are prepared by two‐step melt polycondensation of succinic acid and 1,2‐propanediol with Ti(BuO)4 as the catalyst. By using these PPS‐diols as macroinitiators, the ring‐opening polymerization of d‐ and l‐lactides is readily conducted to obtain enantiomeric ABA triblock copolymers consisting of poly(l‐lactide) and PPS (B) (t‐l‐PPS) as well as those of poly(d‐lactide) and PPS (B) (t‐d‐PPS) which have higher PPS compositions (20–70 wt%) in addition to high molecular weight (20–80 kD). The Tg, Tm, and ΔHm values of the t‐l‐PPS copolymers as well as the stereo mixtures of t‐l‐PPS/t‐d‐PPS are controlled to linearly decrease with increasing the PPS content. The copolymers also exhibit higher elastomeric properties with increasing the PPS content. The tensile properties of the copolymer films having higher PPS contents (both the single block copolymers and stereo mixtures) are comparable to those of the oil‐based thermoplastic elastomers. It is therefore concluded that these block copolymers can afford thermoplastic elastomers or flexible plastic materials having a 100% biobased content.

Synthesis and Self-Assembly of Fully Zwitterionic Triblock Copolymers

Zwitterionic polymers are a distinctive class of materials with unique physical and chemical properties. In this study, the synthesis of fully zwitterionic ABA triblock copolymers was achieved by c...

Controlled synthesis of azobenzene-containing block copolymers both in the main- and side-chain from SET-LRP polymers via ADMET polymerization

Novel ABA triblock copolymer contained azobenzene (azo) chromophores both in the main- and side-chain was designed and synthesized via combination of single electron transfer-living radical polymerization (SET-LRP) and acyclic diene metathesis (ADMET) polymerization. The α-bromoester end group of side-chain azo-polymer prepared in SET-LRP system using acrylate bearing azo group as monomer was reacted with potassium acrylate to yield azo-polymer with the chain end of α-acrylate, which acted as a monofunctional macromolecular chain stopper for subsequent ADMET polymerization of azo-functionalized α,ω-diene monomer to finally controllable synthesize ABA triblock azo-copolymer. The diluted solutions of main-chain ADMET azo-homopolymer, side-chain SET-LRP azo-homopolymer, and main-side chains azo-copolymer exhibited different photoisomerization behaviors (maximum absorption and rate of photoisomerization) under the irradiation of UV and visible light. All these interesting results could provide a guide for the design of photosensitive materials.

Enhanced Flocculation Efficiency in a High-Ionic-Strength Environment by the Aid of Anionic ABA Triblock Copolymers.

The flocculation efficiency of polyelectrolytes in a high-ionic-strength environment is often affected and reduced due to shielding of the active ionizable functional groups, as well as changes in the surface chemistry of the solid slurry. To address this problem, a series of well-defined novel ABA triblock copolymers were employed for the flocculation of high-ionic-strength kaolin slurries at three different Ca2+ concentrations (0.05, 0.10, and 0.50 M). The primary focus was on the advancement in the polymer architecture, where the anionic functionalities were localized at the terminal ends. Typical commercial flocculants tend to have anionic functionalities randomly distributed throughout the polymer chain and hence a higher propensity toward condensed conformation and formation of insoluble species. In comparison to a control random copolymer, the ABA triblock copolymers were able to flocculate kaolin slurries to give faster settlement rates, particularly at the high Ca2+ concentrations of 0.10 and 0.50 M. In addition, these polymers had significantly better clarification ability at higher Ca2+ concentrations compared to the control random copolymer. The ABA triblock copolymer architecture may therefore have potential as a flocculant in high-ionic-strength applications.

Influence of block sequence on the colloidal self-assembly of poly(norbornene)-block-poly(ethylene oxide) amphiphilic block polymers using rapid injection processing

A facile self-assembly method, rapid injection, was used to study the self-assembly difference between AB diblock and ABA triblock copolymers.

Shape-transformation of polymersomes from glassy and crosslinkable ABA triblock copolymers.

Recent developments in the field of polymer vesicles, i.e. polymersomes, have demonstrated that disrupting the equilibrium conditions of the milieu could lead to shape transformation into stable non-spherical morphologies, bringing on-demand shape control to reality and bearing great promise for cell mimicry and a variety of biomedical applications. Here, we studied the self-assembly behavior of glassy amphiphilic triblock copolymers, poly(ethylene glycol)-block-polystyrene-stat-poly(coumarin methacrylate)-block-poly(ethylene glycol) (PEG-b-P(S-stat-CMA)-b-PEG), and their response to various stimuli. By changing the respective molecular weights of both the hydrophobic P(S-stat-CMA) and the hydrophilic PEG blocks, we varied the hydrophobic volume fraction thereby accessing a range of morphologies from spherical and worm-like micelles, as well as polymersomes. For the latter, we observed that slow osmotic pressure changes induced by dialysis led to a decrease in size while rapid osmotic pressure changes by addition of a PEG fusogen led to morphological transformations into rod-like and tubular polymersomes. We also found out that chemically crosslinking the vesicles before inducing osmotic pressure changes led to the vesicles exhibiting hypotonic shock, atypical for glassy polymersomes. We believe that this approach combining the robustness of triblock copolymers and light-based transformations will help expand the toolbox to design ever more complex biomimetic constructs.

A mussel-inspired catecholic ABA triblock copolymer exhibits better antifouling properties compared to a diblock copolymer

The scheme of the chemical architecture, aggregation, assembly and antifouling properties of two copolymers.

A self-healable and antifouling hydrogel based on PDMS centered ABA tri-block copolymer polymersomes: a potential material for therapeutic contact lenses.

Herein we have prepared an antifouling and self-healable poly(dimethyl siloxane) (PDMS) based hydrogel which consists of a mixture of curcumin loaded zwitterionic PDMS polymersomes and amine functionalized PDMS polymersomes prepared via Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization and a Schiff-base reaction. The curcumin loaded polymersome consists of a PDMS and poly([dimethyl-[3-(2-methyl-acryloylamino)-propyl]-(3-sulfopropyl)ammonium)] (poly(sulfobetaine)) based tri-block copolymer (BCP) and it was characterized by dynamic light scattering (DLS), high resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) analyses. To prepare the hydrogel, amine functionalized PDMS polymersomes were crosslinked with polyethylene glycol dialdehyde (PEG-DA) in pH 7.4 buffer solution via a Schiff-base reaction. This hydrogel was able to show sustained delivery of the entrapped curcumin drug for more than 72 h. The self-healing characteristic of the prepared hydrogel in the presence of saline water was elucidated by the "scratch and heal" method and subsequently analyzed through tensile study. Due to the presence of the poly(zwitterionic) moiety in the hydrogel system, it was observed that the hydrogel can efficiently reduce protein deposition, where Bovine Serum Albumin (BSA) was taken as a model protein. It was observed that the curcumin loaded hydrogel was detrimental towards both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria. This type of smart soft hydrogel system can be a potential material for therapeutic applications for several eye diseases.

Dynamic Contributions to the Bulk Mechanical Properties of Self-Assembled Polymer Networks with Reconfigurable Bonds.

Soft materials that contain dynamic and reversible bonds exhibit unique properties including unusual extensibility, reversible elasticity, and self-healing capabilities, for example. Catechol motifs are of particular interest owing to their ability to form many kinds of reversible bonds; however, there are few reports on the role of hydrogen bonds between catechols. Here, physically crosslinked self-assembled networks composed of catechol-functionalized ABA triblock co-polymers are synthesized and characterized to elucidate the role of intermolecular bonding between catechol motifs on bulk mechanical properties. The Young's moduli of equilibrated networks range from 16 to 43 MPa. Furthermore, the concentration of intermolecular interaction is controlled indirectly by synthesizing polymers with prescribed catechol concentrations on each A block. Further, network dynamics are characterized by measuring the relaxation spectrum, and it is found that the network mean relaxation time is inversely related to catechol density. Finally, networks exhibit time-dependent recovery after uniaxial strain. These findings establish important relationships between molecular design, network composition, and macroscopic mechanical properties of model soft matter networks with dynamic intermolecular bonds. Furthermore, this insight has the potential to guide the design of dissipative materials for use in applications ranging from consumer products to surgical materials.

Electrospraying the Triblock Copolymer SEBS: The Effect of Solvent System and the Embedding of Quantum Dots

AbstractThis work reports on ABA triblock copolymer microparticles encoded with CdSe/CdS core–shell quantum dots (QDs) realized by electrospraying. This method allows for simple but efficient embedding of QDs in polymer beads while retaining the fluorescent properties of the original QDs. The creation of poly(styrene‐ethylene‐butylene‐styrene) (SEBS) monodisperse spherical microparticles with a tunable morphology for applications of the final QD‐loaded product is attainable via solvent variation. By varying the selectivity of the solvent for one of the distinct blocks in the polymer, the final particle morphology can be selectively altered while maintaining the same overall process conditions, allowing to tailor the particles from homogeneously flat in a nonselective solvent to dense spherical particles in an endblock selective solvent system. The mechanism responsible for this transition in morphology can be related to differences in mass transfer in the droplets and thus solvent evaporation rates arising from particular microphase structures. Finally, fluorescence characteristics of the final QD‐embedded polymer particles and photodegradation stability are investigated by spectrophotometry and are compared to the temporal evolution of the original QDs, indicating significant stability improvement and well‐dispersed QDs in an optimized polymer matrix morphology.

Recoverably and destructively deformed domain structures in elongation process of thermoplastic elastomer analyzed by graph theory

Thermoplastic elastomer (TPE) by ABA triblock copolymer chains undergoes microphase separation with bridge and loop chains. TPE has a multi-scale structure containing both bridge chain networks and microphase separated structures in meso scale. In the uniaxial elongation process of TPE, coalescence and breaking of domains occur, and an irreversibly deformed structure forms at high strain. To understand the structural changes in an elongation, we performed coarse-grained molecular dynamics simulations of the elongation process of TPE and analyzed the changes of both the bridge chain network and domain structure by graph theory. Both the changes of the domain structures and recombination of bridge chains can be understood by the descriptors of each graph structure. Using the graph description, two types of structures can be found in the elongation process; recoverably and destructively deformed structures. The graph is one of the most useful mathematical descriptors to understand the topology of bridge chain network inside the structures of TPE in the elongation process, including fracture of domains with a microscopic chain conformation.

Photoactivation of Organotellurium Compounds in Precision Polymer Synthesis: Controlled Radical Polymerization and Radical Coupling Reactions

Abstract Organotellurium chain transfer agents (CTAs) used for organotellurium-mediated radical polymerization (TERP) are highly photosensitive and generate radicals by carbon-tellurium bond homolysis upon absorbing UV-vis light at approximately 350–500 nm. The controlled radical polymerization of various vinyl monomers takes place in the presence of organotellurium CTAs under photoirradiation. The use of low-intensity light is important to attain structural control because of the need to maintain a low radical concentration. Photo-TERP not only preserves the synthetic advantages of TERP under thermal conditions, as exemplified by its high versatility in polymerizable monomer families, but also attains new benefits, including decreasing the amount of dead polymers, increasing the control of the macromolecular structure, lowering the polymerization temperature, and providing temporal control. In contrast, irradiation of a polymer prepared by TERP in the presence of dienes and styrenes with high-intensity light selectively gives the dimer via a polymer-end radical coupling reaction. Various symmetrical telechelic and mid-chain-functionalized polymers and ABA-triblock copolymers can be synthesized. Due to the mild conditions for both photo-TERP and the coupling reaction, unique macromolecular structures, and high structural control, these methods provide a new method in macromolecular engineering for fabricating functional polymer materials with improved and/or new functions.

Doubly Charged ABA Triblock Copolymers: Thermomechanically Robust Physical Network and Hierarchical Microstructures

This manuscript describes the structure–property–morphology relationships of doubly charged 1,4-diazabicyclo[2.2.2]octane (DABCO) salt-containing ABA triblock ionomers. The triblock copolymers cons...

Preparation of ABA triblock copolymer assemblies through “one-pot” RAFT PISA

Poly(N,N-dimethyl acrylamide)-block-poly(styrene)-block-poly(N,N-dimethyl acrylamide) (PDMAc-b-PSt-b-PDMAc) amphiphilic triblock copolymer micro/nano-objects were synthesized through reversible addition-fragmentation chain transfer (RAFT) dispersion polymerization of St mediated with poly(N,N-dimethyl acrylamide) trithiocarbonate (PDMAc-TTC-PDMAc) bi-functional macromolecular RAFT agent. It is found that the morphology of the PDMAc-b-PSt-b-PDMAc copolymer micro/nano-objects like spheres, vesicles and vesicle with hexagonally packed hollow hoops (HHHs) wall can be tuned by changing the solvent composition. In addition, vesicles with two sizes (600 nm, 264 nm) and vesicles with HHHs features were also synthesized in high solid content systems (30 wt% and 40 wt%, respectively). Besides, as compared with typical AB diblock copolymers (A is the solvophilic, stabilizer block, and B is the solvophobic block), ABA triblock copolymers tend to form higher order morphologies, such as vesicles, under similar conditions. The finding of this study provides a new and robust approach to prepare block copolymer vesicles and other higher order micelles with special structure via PISA.