Linear Triblock Research Articles

Exploiting Seeded RAFT Polymerization for the Preparation of Graft Copolymer Nanoparticles.

Although seeded reversible addition-fragmentation chain transfer (RAFT) polymerization is explored as a unique method for the preparation of block copolymer nanoparticles with diverse structures, the preparation of nonlinear polymer nanoparticles by seeded RAFT polymerization is rarely reported. Herein, linear block copolymer nanoparticles are first prepared by RAFT dispersion copolymerization of benzyl methacrylate (BzMA) and 2-(2-(n-butyltrithiocarbonate)propionate)ethyl methacrylate (BTPEMA) with different [BzMA]/[BTPEMA] ratios, and employed as seeds for seeded RAFT polymerization of isobornyl acrylate (IBOA) to prepare graft copolymer nanoparticles with different numbers of PIBOA side chains. Comparing with linear triblock copolymers with the same chemical composition, the graft copolymers can promote the formation of higher-order morphologies (e.g., vesicles) under seeded RAFT polymerization conditions. Effects of reaction parameters on the morphology of graft copolymer nanoparticles are investigated in detail, and two morphological phase diagrams are constructed. It is expected that this study will not only expand the scope of seeded RAFT polymerization but also offer new opportunities for the preparation of unique polymer nanoparticles.

Influence of nanoparticles on cylinder-forming linear triblock copolymers

We investigated the influences of nanoparticles on the cylinder-forming triblock copolymers by dissipative particle dynamics (DPD) simulations. We focused on the various aspect ratio and concentrations of the nanoparticles (NPs) with neutral surfaces, where three cases, the nanosphere, nano-ellipsoid and nanorod, were considered. The results indicated that the NPs tend to aggregate in interfaces between the blocks at low NP concentration, but penetrate the cylinder domains when the NP concentration is increased. The shape of NPs has obvious effect on the deforming of cylinder domains, where the NPs with larger aspect ratio are easier to deform the cylinder domains and in turn, their orientations are strongly affected by the polymer chains. These observations provide a deeper understanding of potential applications for microstructures based on complex block copolymers and nanoparticle mixtures.

Multicompartment microparticles of SBM triblock terpolymers: Morphological transitions through homopolymer blending

Block copolymers (BCPs) have recently been explored in spherical confinement to form internally structured microparticles. While the behavior of AB diblock copolymers in confinement is comparably well studied, knowledge on confined ABC triblock terpolymers is still rather sparse. The latter are especially interesting as the third block allows the formation of a broader variety of multicompartment microparticles (MMs), but their synthesis is often realized through sequential polymerization, which can be work intensive and challenging. Here, we demonstrate that blending linear ABC triblock terpolymers with homopolymers is a versatile and straightforward method to tune the microphase behavior in MMs. We systematically blend polystyrene-block-polybutadiene-block-poly(methyl methacrylate) (SBM or PS-b-PB-b-PM) with homopolymers of hPS, hPB, or hPM, to study the feasibility of this approach to replicate specific morphologies or access new ones. We utilize Shirasu Porous Glass (SPG) membrane emulsification and evaporation-induced confinement assembly (EICA) to produce narrowly size-dispersed MMs with defined inner structure. We analyze the MMs with dynamic light scattering (DLS), as well as transmission and scanning electron microscopy (TEM, SEM). We show that the resulting blend morphologies can be identical to those of the unblended SBM at same composition and that, depending on the location in the ternary microphase diagram, one SBM morphology can be converted into multiple different morphologies.Graphical

Visible light-driven photoreforming of polystyrene segmented glycopolymer architectures for enhanced hydrogen generation

In this report, a series of polystyrene segmented new glycopolymer architectures are synthesized, which are utilized in the photoreforming process to achieve a remarkable rate of hydrogen production. The primary building blocks of mono-, bi-, and tetra-functional photo-iniferter were employed in the RAFT polymerization process to design a series of block copolymer architectures using styrene and acetylated glucose methacrylate monomers. Acetylated polymer architectures exhibited higher thermal stability compared to deacetylated polymers. Deacetylated polymers showed lower Tg values than the acetylated polymers. In addition, a wide range of Tg values (55–96 °C) and variations in the Tm values of the acetylated polymers indicate the dependence on the nature of the pendant unit and macromolecular architecture. The deacetylated macromolecule, 1A-PS-b-PGMD diblock copolymer exhibits a hydrogen generation rate of ∼753 μmol/g/h with an AQY of ∼1.84% compared to that of the polystyrene segment alone (53 μmol/g/h, AQY of ∼0.02%). Within the range of possible synthesized glycopolymer architectures, linear and glucose-based triblock glycopolymers show promising activity. The kinetics of the water-splitting reaction are influenced by adjustments to both the solution's pH and the hydrophilicity of the glycomacromolecular chains.

Fundamental Principles and Emerging Opportunities for Selectively‐Solvated Block Copolymer Networks in Nonpolar Media: A Perspective

AbstractBlock polymers remain an extensively studied class of macromolecules due to their ability to self‐organize spontaneously as a result of microphase separation into a variety of ordered nanostructures, depending on the number of contiguous sequences (“blocks”) present and their sequential arrangement. These polymers are classified as multifunctional since they exhibit two or more different property sets during application. In this work, the focus is on bicomponent block copolymers composed of soft and hard segments arranged as linear triblock or higher‐order multiblock copolymers and possessing the properties of a thermoplastic elastomer (TPE). Of particular interest are selectively‐solvated TPEs, designated as TPE gels (TPEGs), with precisely‐ and composition‐tunable properties. An important aspect of TPEs and their TPEG analogs is their elasticity, which reflects the ability of the soft block(s) to form a contiguous molecular network connected by dispersed microdomains composed of the hard block. Here, the origins of microphase separation and network formation in styrenic TPEs and TPEGs are explored, and experimental, theoretical, and simulation results are examined to elucidate chemistry‐structure‐property‐processing (CSPP) relationships in these self‐networking materials. Once such relationships are established, several unconventional technologies that can directly benefit from TPEGs, along with TPEGs fabricated from TPEs possessing different chemical moieties, are likewise considered.

Co-assembly of Amphiphilic Triblock Copolymers with Nanodrugs and Drug Release Kinetics in Solution.

Polymeric vesicles present great potential in disease treatment as they can be featured as a structurally stable and easily functionalized drug carrier that can simultaneously encapsulate multiple drugs and release them on-demand. Based on the dissipative particle dynamics (DPD) simulation, the drug-loaded vesicles were designed by the co-assembly process of linear amphiphilic triblock copolymers and hydrophobic nanodrugs in solvents, and most importantly, the drug release behavior of drug-loaded vesicles were intensively investigated. The drug-loaded aggregates, such as vesicles, spherical micelles, and disk-like micelles, were observed by varying the size and concentration of nanodrugs and the length of the hydrophobic block. The distribution of nanodrugs in the vesicles was intensively analyzed. As the size of the nanodrugs increases, the localization of nanodrugs change from being unable to fully wrap in the vesicle wall to the uniform distribution and finally to the aggregation in the vesicles at the fixed concentration of nanodrugs. The membrane thickness of the drug-loaded polymeric vesicle can be increased, and the nanodrugs localized closer to the center of the vesicle by increasing the length of the hydrophobic block. The nanodrugs will be released from vesicles by varying the interactions between the nanodrug and the solvent or the hydrophobic block and the solvent, respectively. We found that the release kinetics conforms to the first-order kinetic model, which can be used to fit the cumulative release rate of nanodrugs over time. The results showed that increasing the size of nanodrugs, the length of hydrophobic block, and the interaction parameters between the hydrophobic block and the solvent will slow down the release rate of the nanodrug and change the drug release process from monophasic to biphasic release model.

Phase behavior of triblock copolymer and homopolymer blends: Effect of copolymer topology

Two distinct linear triblock copolymers with different block sequences, ABA or BAB, are obtained when two identical AB diblock copolymers are jointed at their B or A ends, respectively, resulting in three homologous, AB diblock, ABA, and BAB triblock copolymers with the same chemical composition but different topologies. We demonstrate that the topological effect on the phase behaviors of these copolymers is amplified when A homopolymers are added to the system. Specifically, the phase behaviors of binary blends composed of ABA or BAB linear triblock copolymers and A homopolymers are studied by using the random-phase approximation (RPA) and self-consistent field theory (SCFT). The RPA analysis predicts that the Lifshitz point for the ABA/A blends behaves like a second-order transition but that for the BAB/A blends behaves like a first-order transition. The Lifshitz point of the BAB/A mixtures is found to occur at a much lower homopolymer concentration than that of the ABA/A mixtures, indicating a poorer miscibility of the A homopolymers into the BAB than ABA triblocks, which is also confirmed by SCFT. For sphere-forming triblock copolymers mixed with homopolymers, the poorer miscibility and the more diffused distribution of the A homopolymers in the BAB/A blends result in a phase behavior drastically different from that of the ABA/A and AB/A blends. The ABA/A blends stabilize the Frank-Kasper (FK) phases similar to the AB/A blends, but the stability window of FK phases becomes negligibly small in the corresponding BAB/A blends. Our results demonstrate that the topological effect of block copolymers on the equilibrium phase behaviors can be more prominent in multicomponent systems and thus more attention should be paid to copolymer topologies in the design of polymeric blends. Published by the American Physical Society 2024

Widening the Application Range of PLA‐Based Thermoplastic Materials through the Synthesis of PLA‐Polyether Block Copolymers: Thermal, Tensile, and Rheological Properties

AbstractPolyethylene glycol (PEG), polypropylene glycol (PPG), and poly(ethylene glycol‐co‐propylene glycol) (PEPG) of number average molar masses (Mn) of 6–20 kDa are used as macroinitiators in the ring‐opening polymerization (ROP) of l‐lactide to synthesize high molar mass (50 kDa < MnCopo < 120 kDa) PLLA‐b‐polyether‐b‐PLLA linear triblock and starblock copolymers. At the studied block lengths, PEG and PEPG blocks exhibit miscibility with the PLLA blocks in the amorphous domains leading to a plasticization effect. As the PEG or PEPG block content is increased to 18 %wt, the Tg (Tg ≈ 24 °C) and the elastic modulus (E ≈ 500 MPa) are reduced, while the elongation at break (εb ≈ 280%) and crystallization rate are increased. At the same time, small angle oscillatory shear (SAOS) rheometric measurements show that the plasticized copolymers have a reduced melt viscosity. In contrast, SAOS and DSC measurements of the PPG‐containing block copolymers reveal phase separation of the PPG and PLA blocks leading to microstructures in the melt. Tensile tests show that the phase‐separated PPG‐containing block copolymers are more ductile than PLA homopolymers, but more brittle than the PEG‐ or PEPG‐plasticized block copolymers.

Photophysical studies of a coumarin derivative in the aqueous solution of three different classes of copolymers

In this article we have reported the modulation of spectral behavior of a hydrophilic coumarin based molecule 7-(diethylamino) coumarin-3-carboxylic acid (7-DCCA) in aqueous solution of polyethylene oxide (PEO)-polypropylene oxide (PPO) block copolymers with different structures and hydrophobicity. Linear triblock copolymer namely Pluronic (F-98, F-38, P-84), its X-shaped counterpart namely Tetronic (T-1304, T-1307) along with a reverse Pluronic (17-R4) were utilised with a temperature variation from 10 °C to 50°C and 7-DCCA was used as the probe to observe the changes in photophysical aspect. Of the studied copolymers, 10 wt% T-1307 and F-38 face difficulty in micelle formation owing to their hydrophilic nature and lower molecular weight PPO blocks. Also, 0.1 wt% 17-R4 remains as single-coils in the studied temperature range. Hence, these copolymers induce a different environment on the photophysics in 7-DCCA as compared to copolymers that form usual micelles (10 wt% T-1304, P-84, F-98). With increasing temperature, a persistent blue-shift in absorption and excitation spectra of the probe could be noticed upon addition of 10 wt% T-1304, T-1307, F-98, P-84, as well as 0.1 wt% 17-R4. The fluorescence emission maximum of the probe blue-shifted in T-1304, T-1307, F-98 and P-84 solutions whereas a red-shift was noticed in 17-R4. The fluorescence emission decays collected in the presence of T-1304, T-1307, F-38, F-98 and P-84 were fitted using tri-exponential functions while bi-exponential functions were used in the presence of 17-R4. A dip-rise-dip anisotropy decay pattern was observed for T-1307, F-38, and 17-R4 whereas, bi-exponential functions were used for T-1304, F-98 and P-84. The constitution of the copolymer along with its molecular properties helped us to correlate the obtained data.

Influence of chain topology on gel formation and direct ink printing of model linear and star block copolymers with poly(ethylene oxide) and poly(ε-caprolactone) semi-crystalline blocks

In this work, a set of well-defined linear triblock copolymers and star block copolymers (3 and 4-arms) with semi-crystalline blocks consisting of poly(ethylene oxide) (PEO) and poly(ε-caprolactone) (PCL), synthesized by combining ring-opening polymerization and organic catalyst switch strategy, were studied as thermosensitive gel-forming biomaterials for applications in 3D extrusion printing. The hydrogels derived from linear copolymers underwent a temperature-dependent sol–gel–sol transition, behaving as a flowing sol at room temperature and transforming into a non-flowing gel upon heating. On the other hand, the hydrogels derived from 4-arm star block copolymers experienced a gel-sol transition and did not flow at room temperature. This behavior allowed them to be used as 3D printing inks at room temperature. 3D printing results revealed that the semi-crystalline hydrogels of the 4-arm star block copolymers could not only be extruded and printed with high shape fidelity, but they also exhibited a favorable dissolution profile for their use as sacrificial biomaterial inks. Additionally, we thoroughly investigated the crystalline organization of the PCL and the PEO blocks within the hydrogels through comparison with the results obtained in bulk. The results demonstrated evident structural ordering in the hydrogels associated with the crystallization of the PCL blocks. Unexpectedly, DSC results combined with SAXS experiments revealed the presence of PEO block crystals within the 30 % w/v hydrogels from 4-arm star block copolymers, in addition to the PCL block crystals. Hence, remarkable double crystalline hydrogels have been obtained for the first time.

CTAB induced growth and shrinkage of Pluronics® P103 micelles: Experimental and theoretical rationale

This study offers an insight into the concentration influence of a cationic surfactant- cetyltrimethylammonium bromide (CTAB) having a 16-carbon long alkyl side chain that influences the self-assembly and micellization behaviour of a linear triblock copolymer based on ethylene oxide (EO) and propylene oxide (PO) Pluronic® P103 in aqueous solution. The work makes an exclusive use of a variety of methodologies, such as high sensitivity differential scanning calorimetry (HSDSC), phase behaviour study, dynamic light scattering (DLS), and small-angle neutron scattering (SANS). The investigation on the clouding behaviour demonstrates that the cloud point value of 5 %w/v P103, which is typically in the vicinity of 90 °C, rises up to more than 100 °C with the addition on of very low concentration of CTAB. The DLS technique predicted the change in hydrodynamic diameter (Dh) of micelles with temperature and in varying CTAB concentration. The SANS results inferred the morphological changes in the micelles. A comprehensive approach revealing the relationship between the molecular orbital energies of the tested P103 and CTAB were assessed by utilising the computational simulation method with the Gaussian 09 calculation window and Gauss View 5.0.9 software. The perception of CTAB-stabilized Pluronics® micelles is predicted to be much improved from the evaluated optimised descriptors. Additionally, our examined micellar system revealed the solubilization enhancement of a model hydrophobic dye orange-OT utilizing UV–vis spectroscopy.

Tuning the morphology of silicon containing copolymers via macromolecular architecture effect

We demonstrate the successful synthesis of linear and non-linear star block copolymers consisting of the highly segregated polystyrene (PS) and poly(dimethylsiloxane) (PDMS) blocks through sequential anionic polymerization combined with chlorosilane chemistry. To study the macromolecular architecture effect on the adopted morphology star block copolymers with six equivalent diblock arms [(PS-b-PDMS)6] were synthesized and compared with their linear diblock copolymer precursors as well as with the corresponding star block copolymers with smaller arm number (2, 3, 4) but identical molecular characteristics. After verifying the molecular and thermal characteristics, bulk studies were carried out through transmission electron microscopy and small angle X-ray scattering. Well-defined structures with enhanced order and similar domain spacing values, irrespective of the architecture complexity of the samples, were observed. The better order of star block copolymers suggests an alternative way to further reduce the lower limit of repeating period by tuning the architecture which is important for the potential future use of the copolymers for nanotechnology related applications. The findings of the specific study are related to the effects of the increased conformational restriction of the inner block. Herein, we show morphological transformations in the (PS-b-PDMS)6 copolymers having non symmetric volume fraction ratios when compared to their linear diblock precursors and triblock copolymers which has not been observed in previous relevant (PS-b-PDMS)n studies that involved stars with less than six arms. To establish the structure/property relationship as a function of arm number, a series of samples involving the diblock precursor, the triblock, the three-, four- and six- arm star block copolymers was prepared, and a systematic comparison was conducted.

Mixed Hyperbranched/Triblock Copolymer Micelle Assemblies: Physicochemical Properties and Potential for Drug Encapsulation

AbstractMixed micelles have numerous advantages while requiring little to no effort in preparation. This study aims to produce mixed micelle nanostructures from a linear triblock copolymer and a hyperbranched random copolymer, and is able to be loaded with the weakly water‐soluble drugs curcumin and indomethacin. Different preparation techniques are employed to produce mixed micelles comprised of Pluronic F127 block copolymer, and hyperbranched poly[(ethylene glycol) methyl ether methacrylate‐co‐lauryl methacrylate], H‐[P(OEGMA‐co‐LMA)], copolymer. Few studies have dabbled in these types of coassemblies, which provides insight into how structural differences of each copolymer can affect the formation of micelles. To determine the properties of the emerging nanostructures in aqueous environments, including their size, homogeneity, and surface charge, different physicochemical techniques are used, such as light scattering and spectroscopic methods. The results reveal that the copolymers combine, and spontaneously self‐assemble into mixed micelle‐like nanostructures in aqueous environments, whereas both systems of neat and drug‐loaded nanostructures exhibit desirable properties such as small average micelle hydrodynamic radii and low size polydispersity indices. The nanostructures that result from the effective encapsulation of curcumin exhibit outstanding stability over 169 days. The fluorescent qualities of curcumin persist after encapsulation, making the novel nanostructures excellent candidates for bioimaging applications.

Self-assembly of ABC-type patchy nanoparticles formed by crosslinking triblock copolymer micelles

Hierarchical self-assembly is efficient in transferring functionality from small to large scales. Polymer nanoparticles with regularity are highly desirable because they are ideal units of hierarchical self-assembly. Herein, we proposed a crosslinking strategy for generating nanoparticles from ABC linear triblock copolymers and conducted a computational study on the self-assembly of the nanoparticles. The effect of nanoparticle symmetry on aggregation behaviors was examined. We found that the symmetric patchy nanoparticles can form various low-curvature aggregates tuned by the crosslinking numbers and A/C block lengths. Increasing the asymmetry of patchy nanoparticles causes the increased curvature of assemblies, forming well-defined structures such as loops, vesicles, and wavy ribbons. Furthermore, the self-assembly kinetics reveals a step-growth nature, resembling the step polymerization for one-dimensional growth. The work demonstrates that ABC-type polymeric nanoparticles are versatile units for building hierarchical assemblies, considerably enriching the self-assembly strategies.

Modeling and Simulation of Linear Triblock Copolymers under Three-Dimensional Confinement

Modeling and Simulation of Linear Triblock Copolymers under Three-Dimensional Confinement

Enhancement of urease properties by introducing new interface based on pH responsive polymer-enzyme bioconjugates via grafting through-RAFT polymerization technique

New interface is introduced to the enzyme by developing the linear triblock copolymer based Polymer- Enzyme Bioconjugates (PEBC) using pH responsive polymer poly (2-acrylamido-2-methylpropane sulfonic acid) (AMPS) with the help of RAFT polymerization technique involving grafting through method. This unique polymeric interface, achieved by designing PEBC employing urease as a model enzyme, has the potential to boost the catalytic properties of commercially important enzymes in robust condition. In PEBC, urease derivative was used which has been immobilized into poly (acrylamide) (PAAm) and poly (2-acrylamido-2-methylpropane sulfonic acid) (PAMPS). Different grades of PEBC were synthesized by changing AMPS amount. PEBC has been characterized by NMR, FT-IR, UV–Vis. spectroscopy, powder XRD, SEM, TGA, CMC, pH-CMC, DLS, and GPC. Urea-Urease hydrolysis kinetics in buffer medium was used to examine stability over a long period of time at different pH and temperature conditions for free urease and urease enzyme present in PEBC and its catalytic activities have been verified with the help of Michaelis-Menten kinetic constant (Km). Due to a similar km value, the PEBC bonded enzyme has approximately same affinity as the free enzyme when compared. In conclusion, this technique successfully stabilizes enzymes throughout a pH range for a number of practical applications.

Improved Route to Linear Triblock Copolymers by Coupling with Glycidyl Ether-Activated Poly(ethylene oxide) Chains.

Poly(ethylene oxide) block copolymers (PEOz BCP) have been demonstrated to exhibit remarkably high lithium ion (Li+) conductivity for Li+ batteries applications. For linear poly(isoprene)-b-poly(styrene)-b-poly(ethylene oxide) triblock copolymers (PIxPSyPEOz), a pronounced maximum ion conductivity was reported for short PEOz molecular weights around 2 kg mol-1. To later enable a systematic exploration of the influence of the PIx and PSy block lengths and related morphologies on the ion conductivity, a synthetic method is needed where the short PEOz block length can be kept constant, while the PIx and PSy block lengths could be systematically and independently varied. Here, we introduce a glycidyl ether route that allows covalent attachment of pre-synthesized glycidyl-end functionalized PEOz chains to terminate PIxPSy BCPs. The attachment proceeds to full conversion in a simplified and reproducible one-pot polymerization such that PIxPSyPEOz with narrow chain length distribution and a fixed PEOz block length of z = 1.9 kg mol-1 and a Đ = 1.03 are obtained. The successful quantitative end group modification of the PEOz block was verified by nuclear magnetic resonance (NMR) spectroscopy, gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). We demonstrate further that with a controlled casting process, ordered microphases with macroscopic long-range directional order can be fabricated, as demonstrated by small-angle X-ray scattering (SAXS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It has already been shown in a patent, published by us, that BCPs from the synthesis method presented here exhibit comparable or even higher ionic conductivities than those previously published. Therefore, this PEOz BCP system is ideally suitable to relate BCP morphology, order and orientation to macroscopic Li+ conductivity in Li+ batteries.

Star-Shaped Thermoplastic Elastomers Prepared via RAFT Polymerization.

Styrene-based thermoplastic elastomers (TPEs) demonstrate excellent overall performance and account for the largest industrial output. The traditional methods of preparation styrene-based thermoplastic elastomers mainly focused on anionic polymerization, and strict equipment conditions were required. In recent years, controlled/living radical polymerization (CRP) has developed rapidly, enabling the synthesis of polymers with various complex topologies while controlling their molecular weight. Herein, a series of core crosslinked star-shaped poly(styrene-b-isoprene-b-styrene)s (SISs) was synthesized for the first time via reversible addition-fragmentation chain transfer (RAFT) polymerization. Meanwhile, linear triblock SISs with a similar molecular weight were synthesized as a control. We achieved not only the controlled/living radical polymerization of isoprene but also investigated the factors influencing the star-forming process. By testing the mechanical and thermal properties and characterizing the microscopic fractional phase structure, we found that both the linear and star-shaped SISs possessed good tensile properties and a certain phase separation structure, demonstrating the characteristics of thermoplastic elastomers.

Thermal and Bulk Properties of Triblock Terpolymers and Modified Derivatives towards Novel Polymer Brushes.

We report the synthesis of three (3) linear triblock terpolymers, two (2) of the ABC type and one (1) of the BAC type, where A, B and C correspond to three chemically incompatible blocks such as polystyrene (PS), poly(butadiene) of exclusively (~100% vinyl-type) -1,2 microstructure (PB1,2) and poly(dimethylsiloxane) (PDMS) respectively. Living anionic polymerization enabled the synthesis of narrowly dispersed terpolymers with low average molecular weights and different composition ratios, as verified by multiple molecular characterization techniques. To evaluate their self-assembly behavior, transmission electron microscopy and small-angle X-ray scattering experiments were conducted, indicating the effect of asymmetric compositions and interactions as well as inversed segment sequence on the adopted morphologies. Furthermore, post-polymerization chemical modification reactions such as hydroboration and oxidation were carried out on the extremely low molecular weight PB1,2 in all three terpolymer samples. To justify the successful incorporation of -OH groups in the polydiene segments and the preparation of polymeric brushes, various molecular, thermal, and surface analysis measurements were carried out. The synthesis and chemical modification reactions on such triblock terpolymers are performed for the first time to the best of our knowledge and constitute a promising route to design polymers for nanotechnology applications.

Effects of ionic strength and ion-specificity on the interface behavior of PDMAEMA-b-PLMA-b-POEGMA triblock terpolymer

Ion-specificity on the stretching degree of diblock copolymers containing poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) at the air/water interface has previously been proved to be inconsistent with the Hofmeister series. In this work, the aggregation behavior of an amphiphilic linear triblock terpolymer poly[2-(dimethylamino)ethyl methacrylate]-block-poly(lauryl methacrylate)-block-poly[oligo(ethylene glycol) methacrylate] (PDMAEMA-b-PLMA-b-POEGMA) on the aqueous subphase with different ionic strengths and ion species (salts) was studied, and the morphologies of its Langmuir−Blodgett (LB) films were explored. At the air/water interface, the terpolymer tends to form surface micelles composed of hydrophobic PLMA cores and mixed hydrophilic coronas of PDMAEMA and POEGMA. Under acidic conditions with low ionic strength, the hydrophilic PDMAEMA blocks of the terpolymer are almost completely electrostatic screened. With the increase of subphase ionic strength, the surface pressure−molecular area isotherms of the terpolymer monolayers at the air/water interface gradually move to large areas due to the increased interfacial stretching degree of POEGMA blocks resulting from the increased salting-out effect and interfacial steric hindrance of PDMAEMA blocks. The hysteresis degrees of the terpolymer monolayers in the presence of salts in the subphase are larger than that in the absence of salt. Under alkaline conditions, the isotherms of the terpolymer monolayers move to large areas with the increase of salt concentration because the introduction of salt makes the hydrophilic blocks more stretched. The experimental results show that the relationship between their interfacial stretching degrees of two kinds of hydrophilic blocks and the types of salt in solution is inconsistent with the Hofmeister series. This may be due to tethering of the corona chains on the hydrophobic core and the configurational constrains (crowding phenomena) induced within the mixed micelle corona. Under different subphase conditions, the LB films of the terpolymer show isolated circular micelles due to the mutual repulsions of the long hydrophilic PDMAEMA and POEGMA blocks.