Type Triblock Copolymers Research Articles

Polymer membrane based on ABC type triblock co-polymer for safer lithium-ion solid-state batteries

Polymer membrane based on ABC type triblock co-polymer for safer lithium-ion solid-state batteries

Synthesis and properties of ABA type triblock copolymer from poly(dimethylsiloxane) macroinitiator: Development of novel attachable initiators for atom transfer radical polymerization

A sequence of ABA-type polystyrene-b-poly(dimethylsiloxane)-b-polystyrene (PS-b-PDMS-b-PS) triblock copolymers were synthesized by ATRP (Atom Transfer Radical Polymerization) after appropriate end functionalization of vinyl terminated PDMS. Vinyl terminated PDMS was reacted with a 3-chloropropane thiol to synthesize a halo terminated macroinitiator. Subsequently, this macroinitiator was used to synthesize ABA-type block copolymers. The resulting block copolymers were characterized to confirm the presence of PDMS & PS blocks. The theoretical molecular weight and GPC was used to verify the high molecular weight of the ultimate block copolymer. The results show that the PS chains were successfully bound to the PDMS backbone and molecular weight linearly increased with time during the controlled polymerization. The functionality of the given polymer was confirmed by FT-IR analysis, 1H NMR, and 13C NMR spectra. The thermal stability increased after the addition of PS with PDMS. Additionally, the EDS analysis confirms the halogen content. DLS verified the particle size, whereas SEM was used for the morphology of the nanoaggregates. This triblock has good moisture resistance & thermal stability as determined by thermogravimetric analysis. The formation of PDMS blocks increased the hydrophobicity of the PS and contact angle analysis confirmed this.

Synthesis of an ABC triblock copolymer by a bilateral Click reaction using α,ω-bifunctionalized poly(3-hexylthiophene) as an inner segment

A novel A-b-poly(3-hexylthiophene)(P3HT)-b-C type triblock copolymer was successfully synthesized by the bilateral Cu-catalyzed azide alkyne cycloaddition reaction using α,ω-bifunctionalized P3HT.

Polyethylene glycol-based RAFT agent cum ATRP macroinitiator initiated block copolymerization of methyl methacrylate

PMMA-b-PEG-b-PMMA block copolymer has been synthesized by the activators regenerated by electron transfer atom transfer radical polymerization (ARGET-ATRP) of methyl methacrylate (MMA) using modified polyethylene glycol (PEG) as initiator. PEG is chemically modified by CS2 followed by an esterification to incorporate initiating sites for ATRP as well as for RAFT polymerization. The prepared macroinitiator has been characterized by FT-IR and NMR analyses for its structural validation. FT-IR and NMR analyses confirmed the successful synthesis of the macro initiator. This macro initiator has been used to prepare ABA type triblock copolymer with MMA via ARGET-ATRP. The polymerization reaction is carried out using cupric bromide (CuBr2) as catalyst in combination with N,N,N′,N″,N″-pentamethyl diethylenetriamine (PMDETA) as ligand in N, N dimethyl formamide (DMF) at 70C. Ascorbic acid is used as reducing agent. The conversion of the monomer was calculated gravimetrically. The successful preparation of the block copolymer is confirmed by FT-IR, 1H NMR and 13C NMR analyses. The MALDI-TOF mass analysis of the block copolymers also confirm the presence of monomer MMA, dithionate and PEG parts in the block copolymer. The purified block copolymer is analyzed by TGA, and SEM analyses. TGA analysis shows that the prepared block copolymer has better (Tmax = 366C) thermal stability than the PMMA (Tmax = 349C) homopolymer.

Highly Stretchable Semiconducting Polymers for Field-Effect Transistors through Branched Soft–Hard–Soft Type Triblock Copolymers

In this study, poly(3-hexylthiophene)-block-poly(δ-decanolactone)s (P3HT-b-PDLs) with the molecular architecture of AB, BAB, B2AB2, and B3AB3 (A: P3HT, B: PDL) were synthesized for stretchable orga...

Initiating Mechanism of the Anionic Polymerization of Methacrylates with t‐BuOK and the Synthesis of ABA Type Triblock Copolymers

Initiating Mechanism of the Anionic Polymerization of Methacrylates with <i>t</i>‐BuOK and the Synthesis of ABA Type Triblock Copolymers

Initiating Mechanism of the Anionic Polymerization of Methacrylates with t‐BuOK and the Synthesis of ABA Type Triblock Copolymers

AbstractUsing potassium tert‐butoxide (t‐BuOK) as initiator, anionic polymerization and copolymerization of the methacrylate monomers are carried out in tetrahydrofuran at 0 °C or above. The polymers are characterized by gel permeation chromatography (GPC), proton nuclear magnetic resonance (1H‐NMR), Fourier transform infrared (FTIR), and dynamic mechanical analyzer (DMA). There is a critical concentration of the active species in t‐BuOK, above which no matter how much more t‐BuOK is added, it has no initiation activity. Among the active species of t‐BuOK, the main part possesses large average vibration distance between anion–cation pairs, which can initiate all methacrylate monomers in this study. While another part of the active species possesses the small average vibration distance, which can only initiate the polymerization of methyl methacrylate at slow rate. It provides an supporting evidence for the “channel idea” proposed previously. Finally, poly(methyl methacrylate)‐b‐poly(lauryl methacrylate)‐b‐poly(methyl methacrylate) (PMMA‐b‐PLMA‐b‐PMMA) three‐block copolymer is synthesized. This study paves the way for the synthesis of thermoplastic elastomers with full polar monomers and full saturated chains by anionic polymerization.

Synthesis of Block Copolymers of Polyester and Polystyrene by Means of Cross-Metathesis of Cyclic Unsaturated Polyester and Atom Transfer Radical Polymerization

Synthesis of B–A–B type triblock copolymers of aliphatic polyester (PEs) and polystyrene (PSt) was investigated by using cyclic unsaturated PEs prepared by conventional polycondensation of 4-octene-1,8-diol and sebacoyl chloride. The obtained cyclic PEs underwent cross-metathesis with PSt containing a carbon–carbon double bond (C═C) at the central position, which was obtained by atom transfer radical polymerization (ATRP) of styrene with a bifunctional initiator containing a C═C bond. PSt with a longer methylene spacer between the C═C bond and PSt successfully afforded the PSt-b-PEs-b-PSt triblock copolymer. As another approach to obtain the triblock copolymer, cross-metathesis of cyclic PEs with 2-butene-1,4-diol or 4-octene-1,8-diol bis(2-bromoisobutyrylate)s was conducted to afford linear PEs having ATRP initiation sites at both ends, followed by ATRP of styrene. The unsaturated PEs segment in the triblock copolymer obtained by the second approach was converted into a saturated PEs segment by treatment...

Interaction of salicylic acid analogues with Pluronic® micelles: Investigations on micellar growth and morphological transition

The aqueous solutions of PEO-PPO-PEO type triblock copolymers (Pluronic® P123, P103 and P105) with variations in their total molecular weight and block contribution are investigated for encapsulation of drugs. Two drugs, namely Aspirin (AS) and 5-Methyl Salicylate (MS) having different partition coefficient was studied. The changes in size and micellar dynamics due to formation of drug-polymer complexes are investigated using dynamic light scattering (DLS), dynamic surface tension (DST), Nuclear Magnetic Resonance (NMR) and Small angle neutron scattering (SANS) measurements. Increase in apparent hydrodynamic diameter (Dh) measured by DLS suggests the growth of micelles, which is equally supported by calculated micellar parameters from SANS measurements. The solubilization of drugs within micelles alters the diffusivity of the monomers due to stronger hydrophobic forces leading to highly stable aggregates as concluded by dynamic surface tension measurements. The significant increase in micellar size was noticed in presence of MS, while AS had less prominent effect on micellar growth. The preferential partitioning of drug into the hydrophobic micellar core is the driving force for the possible formation of higher morphologies. The hydrophobic interactions between MS and P123 are confirmed by 1H NMR. The differences in molecular interactions leading to distinct morphological behavior are explained by the localization of drug within nanocarriers.

Mesopore Connectivity Improving Aerosol-Assisted Synthesis of Mesoporous Alumina Powders with High Surface Area.

Considering the closed packing of supramolecular mediated cage-type (spherical) mesopores inside spherical particles that are typically obtained by the aerosol-assisted process, uniform mesopores cannot be packed so periodically and then the mesopores are less connected and/or occasionally isolated, leading to the formation of low-surface-area mesoporous particles. In this study, we proposed the controlled swelling of such cage-type mesopores for improving their connectivity. Actually, we succeeded in preparing high-surface-area mesoporous alumina powders using poly(oxyethylene)- block-poly(oxypropylene)- block-poly(oxyethylene) (EO nPO mEO n) type triblock copolymers such as Pluronic P123. The surface area of the mesoporous alumina powders was originally low (278 m2 g-1 without organic additives), which can be drastically increased up to ca. 540 m2 g-1 through the controlled welling with suitable addition of 1,3,5-trimethylbenzene and 1,3,5-triisopropylbenzene. The insight is promising for further development of the aerosol-assisted approach for recovering high-quality mesoporous powders and helpful for rational catalyst design by utilizing mesoporous alumina powders with extremely high surface area.

Effect of molecular weight and diffusivity on the adsorption of PEO-PPO-PEO block copolymers at PTFE-water and oil-water interfaces

The diffusion and adsorption behaviors of a few PEO-PPO-PEO type triblock copolymers, namely, Pluronics® L62, L64, F68, F87, and F88 at solid-liquid and liquid-liquid interfaces is investigated using water penetration through packed PTFE powder, dynamic surface tension (DST), interfacial tension (IFT), dynamic light scattering (DLS), and contact angle measurements. The water penetration and DST data reveal that the diffusivity of these block copolymers to the interface decreases with increase in the PEO molecular weight of the polymer and is governed by adsorption of surfactant molecules at the interface through PPO blocks. The DST and IFT results reveal faster diffusion to the interface for low molecular L62 and L64. The adsorption behaviors at isopropyl myristate (IPM)-water and PTFE-water interfaces are in good agreement, where lower molecular weight and lower PEO content favor the faster diffusion kinetics. The size of the formed emulsion droplets in presence of different surfactant molecules is measured using DLS, which shows bigger emulsion droplet size for high molecular weight and PEO containing polymer F88. Thus, it was found that surfactant having lower DST will result in higher wettability, lower contact angle, and lower interfacial tension.

Reverse Hexosome Dispersions in Alkanes-The Challenge of Inverting Structures.

Monoglycerides form lipophilic liquid-crystalline (LC) phases when mixed with water. The corresponding LC nanostructures coexist with excess water, which is a necessary condition for the formation of internally nanostructured dispersed particles. These nanostructures comprise bicontinuous cubic phases, inverted hexagonal phases, and inverted micellar cubic phases. The dispersed particles are therefore named cubosomes, hexosomes, or micellar cubosomes. Such dispersions are usually stabilized by hydrophilic high-molecular-weight triblock (TB) copolymers. Another way to stabilize such dispersions is by forming the so-called Pickering or Ramsden emulsions using nanoparticles as stabilizers. In this contribution, we explore the possibility of forming and stabilizing inverted or reverse systems, that is, dispersions of hydrophilic LC phases in an excess oil phase like tetradecane. Our aim was to change from oil-in-water emulsions to water-in-oil emulsions, where the water phase is a LC phase in equilibrium with excess oil and where the oil is nonpolar, for example, an alkane. This work consists of three parts: (1) to find a hexagonal hydrophilic LC phase that can not only incorporate a certain amount of tetradecane but can also coexist with excess tetradecane in the case of higher oil concentration, (2) to find a suitable stabilizer-either polymeric or nanoparticle type-that can stabilize the emulsion without destroying the hexagonal LC phase, and finally (3) to check the stability of this reverse hexosome emulsion. We discovered that it is possible to create a hexagonal hydrophilic LC phase with short-chain nonionic surfactants such as polyethylene glycol alkyl ethers or with high-molecular-weight TB copolymers of type A-B-A. Furthermore, it is possible to successfully stabilize the reverse hexosomes with low hydrophilic-lipophilic balance TB copolymers-either synthesized in our laboratory or commercially available ones-as well as with hydrophobized, commercially available silica nanoparticles.

Synthesis of Poly(N-H benzamide)-b-poly(lauryl methacrylate)-b-poly(N-H benzamide) symmetrical triblock copolymers by combinations of CGCP, SARA ATRP, and SA ATRC

We design a novel ABA type triblock copolymer (triBCP) by performing efficient synthetic methods of chain-growth condensation polymerization (CGCP), supplemental activator and reducing agent atom transfer radical polymerization (SARA ATRP), and styrenics-assisted atom transfer radical coupling (SA ATRC). A well-defined poly(3-(N-(octyloxy)benzyl benzamide) having a 2-bromo-2-phenylacetate effective ATRP initiating site (i.e., POOBBA-BrPA) through CGCP following quantitative chain end modifications, was firstly synthesized. The POOBBA-BrPA macroinitiator then conducted chain extension with lauryl methacrylate (LMA) via SARA ATRP to obtain the POOBBA-b-PLMA-Br diBCP (Mn = 8800 and Mw/Mn = 1.15). This was followed by SA ATRC of POOBBA-b-PLMA-Br with a high extent of coupling (xc = 0.85, Mn = 15300, and Mw/Mn = 1.26). The obtained triBCP was further purified and the selective removal of the protecting group yielded poly(N-H benzamide)-b-poly(lauryl methacrylate)-b-poly(N-H benzamide) (i.e., PNHBA-b-PLMA-b-PNHBA) was conducted. The characterization of these copolymers was performed using 1H NMR, GPC, FT-IR, TGA, DSC, AFM and SAXS.

Combination of Photoinduced ATRP and Click Processes for the Synthesis of Triblock Copolymers

ABA type triblock copolymers possessing polystyrene as middle segment and poly(ε-caprolactone) (PCL) and poly(ethylene glycol) (PEG) as side segments were synthesized by combining two photochemical strategies, namely photoinduced atom transfer radical polymerization (ATRP) and click processes. For this purpose, α,ω-diazido functional polystyrene (N3-PS-N3) was synthesized by photoinduced ATRP using a bifunctional initiator, followed by a simple substitution of the chain end halides. Parallel to this, alkyne-PCL was synthesized by ring opening polymerization of ε-caprolactone, employing propargyl alcohol as initiator. For the synthesis of alkyne-PEG, industrially available PEG was functionalized by a simple esterification reaction using 5-pentynoic acid. After the syntheses of these alkyne functional polymers as clickable counterparts, they were reacted with N3-PS-N3 by photoinduced click reactions to prepare the desired triblock copolymers. All polymers were characterized by NMR, IR and GPC analyses.

Effect of poly(l-lactide) chain length on microstructural and thermo-mechanical properties of poly(l-lactide)-b-poly(butylene carbonate)-b-poly(l-lactide) triblock copolymers

A series of ABA type triblock copolymers based on biodegradable poly(butylene carbonate) (PBC) and poly(l-lactide) (PLLA) were synthesized with PBC as the core and varying the PLLA chain length. A significant reduction in the crystallinity of the PBC component is observed in the block copolymers as evidenced by DSC and wide angle X-ray diffraction. A systematic increase in the crystallinity of the PLLA blocks is also observed with increasing chain length of PLLA. The block copolymers undergo a transition from micro-phase separated lamellar morphology to macro-phase separated unstable morphology in the composition domain of ∼45–55 wt% of PLLA. A pseudo-ductile to quasi-brittle transition was observed in the composition range of ∼45–55 wt% of PLLA corresponding to a change in morphology as confirmed by Atomic Force Microscopy and Small Angle X-ray Scattering. This study demonstrates a green path for PLLA toughening by using another biodegradable aliphatic polymer.

Synthesis of an ABC Type Triblock Copolymer on MWCNT Surface: Structural, Thermal, Electrical and SEM Characterization

Abstract : Multi-walled carbon nanotubes (MWNTs) attached to ethylene glycol (MWNT-OH) were grafted with ring-opening polymerization of e-caprolactone (MWNT-pCL). Initiating sites for atom transfer radical polymerization (ATRP) were formed by end acylation of MWNT-pCLwith α-bromopropionyl bromide. After styrene was polymerized by ATRP on the surface of the macroinitiator (MWNT-pCL-Br) in presence of CuBr/2,2′-bipyridine as catalyst at 110 o C, the triblock copolymer (MWNT-pCL-b-PS-b-pGMA) was prepared by the aid of the same technique using glycidyl methacrylate as monomer, at the same catalyst and temperature conditions, by using the diblock copolymer (MWNT-pCL-b-PS) as macroinitiator. The 1 HNMR studies show that structure in terms of mer number per molecule of the ABC type triblock copolymer is MWNT-p(CL) 6 - b -P(S) 36 - b -p(GMA) 1080 . The determination of chemical structure of the triblock copolymer was carried out using Fourier transform infrared (FT-IR), proton nuclear magnetic resonance ( 1 H NMR) and scanning electron microscopy (SEM). Thermal properties were investigated by using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The Tg value estimated from the temperature dependence of the dielectric constant, the dielectric loss factor, and the ac conductivity for the triblock copolymer, is in agreement with the DSC value. The results of the dielectric constant and ac conductivity of the triblock copolymer were also discussed.

Self-Assembly of Thermoreversible Hydrogels via Molecular Recognition toward a Spatially Organized Coculture System.

In this study, we present the spontaneous adhesion of two thermoreversible physically cross-linked hydrogels via molecular recognition under a physiological condition. We successfully prepared two types of hydrogels generated using two kinds of well-defined ABA type triblock copolymers: CAT-ABA and PBA-ABA, which contain catechol and phenylboronic acid groups as functional side chains, respectively. Both types of ABA triblock copolymers were able to undergo sol-to-gel transition with the increase in temperature resulting from the formation of physical cross-links at a physiological temperature, which enables easy cell encapsulation in the hydrogel. It was determined that the cell encapsulating hydrogels exhibited spontaneous macroscopic adhesion through the formation of boronic esters between phenylboronic acid and catechol at the hydrogel interface. This novel system likely represents a promising method to construct a precisely organized, three-dimensional coculture system to enable the reconstruction of complicated tissues such as the liver in vitro.

Temperature- and pH-dependent aggregation behavior of hydrophilic dual-sensitive poly(2-oxazoline)s block copolymers as latent amphiphilic macromolecules

A variety of hydrophilic diblock and triblock copolymers of AB and ABA type with temperature-sensitive poly(2-isopropyl-2-oxazoline) blocks und pH-sensitive poly(2-carboxyethyl-2-oxazoline) blocks have been synthesized. The temperature- and pH-induced reversible phase transition renders the block copolymers as amphiphilic macromolecules and allows for defined aggregation through self-assembly following the packing parameter of amphiphilic macromolecules. Size, structure and arrangement of the individual block copolymer segments define the temperature and pH values of the transitions as well as the nature of the formed aggregates. DLS measurements were used to determine the transition temperatures at selected pH values in aqueous solution whereas AFM was used to visualize and characterize the formed aggregates adsorbed on Si wafer surfaces. In the case of vesicles formed by the diblock and triblock copolymers, double and monolayer membranes could be verified. The tendency of different states of organization of poly(2-isopropyl-2-oxazoline) blocks from crystalline to amorphous is assumed to be the cause for the different box-like structures determined on Si wafer surfaces.

Synthesis of benzoin end-chain functional macrophotoinitiator of poly(d,l-lactide) homopolymer and poly(ε-caprolactone)-poly(d,l-lactide) diblock copolymer by ROP and their use in photoinduced free radical promoted cationic copolymerization

Benzoin (B) end-chain functional macrophotoinitiator of poly(d,l-lactide) homopolymer (B-PDLLA) and poly(e-caprolactone)-poly(d,l-lactide) (B-PCL-b-PDLLA) diblock copolymer with controlled molecular weights and low polydispersities have been synthesized via ring-opening polymerization (ROP). The ROP of d,l-lactide with benzoin as the initiator and tin octoate (Sn(Oct)2) as the catalyst in bulk at 130 °C formed B-PDLLA polymer. B-PCL-b-PDLLA was synthesized by sequential ROP in two steps. Benzoin (B) end-chain functional macrophotoinitiator of poly(e-caprolactone) (B-PCL) was first prepared via ROP of e-caprolactone by using benzoin/Sn(Oct)2 initiating system. The resultant hydroxyl-terminated B-PCL macrophotoinitiator was subsequently utilized as the macroinitiator in the second-step ROP of d,l-lactide to synthesize B-PCL-b-PDLLA. The 1H NMR, FT-IR, GPC, UV, and fluorescence spectroscopic studies revealed that low-polydispersity poly(d,l-lactide) homopolymer and poly(e-caprolactone)-poly(d,l-lactide) diblock copolymer with benzoin end-groups were obtained. These macrophotoinitiators were used as prepolymers in photoinitiated free radical promoted cationic polymerization for obtaining AB type di- and ABC type tri-block copolymers.

Strategic synthesis of mesoporous Pt-on-Pd bimetallic spheres templated from a polymeric micelle assembly

Core–shell–corona type triblock copolymer poly(styrene-b-2-vinylpyridine-b-ethylene oxide) (PS-b-P2VP-b-PEO) micelles have been selected here to direct the synthesis of mesoporous Pt-on-Pd spheres.