Tetrablock Copolymers Research Articles

Synthesis and Characterization of All-Acrylic Tetrablock Copolymer Nanoparticles: Waterborne Thermoplastic Elastomers via One-Pot RAFT Aqueous Emulsion Polymerization.

Reversible addition-fragmentation chain transfer (RAFT) aqueous emulsion polymerization is used to prepare well-defined ABCB tetrablock copolymer nanoparticles via sequential monomer addition at 30 °C. The A block comprises water-soluble poly(2-(N-acryloyloxy)ethyl pyrrolidone) (PNAEP), while the B and C blocks comprise poly(t-butyl acrylate) (PtBA) and poly(n-butyl acrylate) (PnBA), respectively. High conversions are achieved at each stage, and the final sterically stabilized spherical nanoparticles can be obtained at 20% w/w solids at pH 3 and at up to 40% w/w solids at pH 7. A relatively long PnBA block is targeted to ensure that the final tetrablock copolymer nanoparticles form highly transparent films on drying such aqueous dispersions at ambient temperature. The kinetics of polymerization and particle growth are studied using 1H nuclear magnetic resonance spectroscopy, dynamic light scattering, and transmission electron microscopy, while gel permeation chromatography analysis confirmed a high blocking efficiency for each stage of the polymerization. Differential scanning calorimetry and small-angle X-ray scattering studies confirm microphase separation between the hard PtBA and soft PnBA blocks, and preliminary mechanical property measurements indicate that such tetrablock copolymer films exhibit promising thermoplastic elastomeric behavior. Finally, it is emphasized that targeting an overall degree of polymerization of more than 1000 for such tetrablock copolymers mitigates the cost, color, and malodor conferred by the RAFT agent.

Cyclic and Linear Tetrablock Copolymers Synthesized at Speed and Scale by Lewis Pair Polymerization of a One-Pot (Meth)acrylic Mixture and Characterized at Multiple Levels.

Cyclic block copolymers (cBCP) are fundamentally intriguing materials, but their synthetic challenges that demand precision in controlling both the monomer sequence and polymer topology limit access to AB and ABC block architectures. Here, we show that cyclic ABAB tetra-BCPs (cABAB) and their linear counterpart (lABAB) can be readily obtained at a speed and scale from one-pot (meth)acrylic monomer mixtures, through coupling the Lewis pair polymerization's unique compounded-sequence control with its precision in topology control. This approach achieves fast (<15 min) and quantitative (>99%) conversion to tetra-BCPs of predesignated linear or cyclic topology at scale (40 g) in a one-pot procedure, precluding the needs for repeated chain extensions, stoichiometric addition steps, dilute conditions, and postsynthetic modifications, and/or postsynthetic ring-closure steps. The resulting lABAB and cABAB have essentially identical molecular weights (Mn = 165-168 kg mol-1) and block degrees/symmetry, allowing for direct behavioral comparisons in solution (hydrodynamic volume, intrinsic viscosity, elution time, and refractive indices), bulk (thermal transitions), and film (thermomechanical and rheometric properties and X-ray scattering patterns) states. To further the morphological characterizations, allylic side-chain functionality is exploited via the thiol-ene click chemistry to install crystalline octadecane side chains and promote phase separation between the A and B blocks, allowing visualization of microdomain formation.

Precise Synthesis of Tetrablock Copolymers of Different Acrylamide Derivatives via Iterative Aqueous Cu(0)-Mediated Polymerization

The accessibility of specific synthesis of tetrablock copolymers is reported. In a specific synthesis, four acrylamide monomers are gradually added using an iterative aqueous Cu(0)-mediated reversible-deactivation radical polymerization (RDRP) method. Essential to the success of this approach is the ability to design and polymerize ABCD copolymer sequence with no need for immediate purification steps. The simple in-situ sequential polymerization method allowed for essentially perfect control of accurately well-defined tetrablock copolymers, which are composed of four tiny blocks, each of which contains an average of ten functional monomer units of acrylamide derivatives, resulting in a variety of functional groups. While the final molecular weight distributions have very narrow despersities (Đ &lt; 1.10), the efficient successive chain extension polymerization proceeded with high monomer conversions (&gt;99%), delivering excellent block purification in a short period of time. The tetrablock poly(NIPAM-DMA-HEAA-DEA) was characterized by NMR and GPC and showed beneficial end-group fidelity, allowing quantitative monitoring of the system’s alive nature after each synthetic cycle. Importantly, these one-pot syntheses are carried out at a below temperature of 0.0 °C in water as the solvent and can be implemented for applications of molecular biology. We also investigate the potential for a copper-amide complex to develop with acrylamide monomer, which could have an adverse effect on the end group’s functioning. Finally, we believe that this approach makes it easier to create a novel category of advanced polymeric materials.

Facile synthesis of asymmetric tetrablock copolymer by dual thermal and photochemical initiator

Vesicles obtained by the self-assembly of asymmetric tetrablock copolymers are a class of materials with fascinating properties. However, simple strategies to synthesize asymmetric tetrablock copolymers are limited. Herein, we have designed and synthesized an initiator which generates radicals by either heating or photoirradiation. Taking the advantages of organocatalyzed reversible complexation mediated radical polymerization which has lower energy requirements, milder reaction conditions, and reduced generation of hazardous byproducts, a three steps synthetic route following “photo-photo-thermal” initiation condition for the preparation of asymmetric CABC tetrablock copolymers with controllable molecular weight, precise block composition and low polydispersity was developed.

Dynamic Monte Carlo Simulations of Strain-Induced Crystallization in Multiblock Copolymers: Effects of Asymmetric Block Rigidity.

Thermoplastic elastomers such as polyether-b-polyamides (or -polyesters), polyurethanes (or with -urea) and olefin block copolymers are commonly processed through a stretching process for achieving high elasticity and high toughness in their products, while the size diversity of semicrystalline microdomains of hard blocks appears as the key factor. By means of dynamic Monte Carlo simulations of strain-induced crystallization of locally concentrated and diluted crystallizable blocks alternatingly connected with noncrystallizable blocks in diblock and tetrablock copolymers, we have studied the size diversity of semicrystalline microdomains presumably raised by local concentration fluctuations of crystallizable blocks and found the dilution effects to persist from diblock to tetrablock copolymers. In the present work, we continued to study the effects of asymmetric block rigidity between crystallizable and noncrystallizable blocks on strain-induced crystallization of concentrated and diluted crystallizable blocks in diblock copolymers. The results showed that when crystallizable blocks hold higher thermodynamic rigidity than noncrystallizable blocks, the large semicrystalline domains become larger and the small semicrystalline domains become more, enhancing their size diversity. However, asymmetric kinetic rigidity has little effect. Our observations imply that industrial stretching processing could enhance the toughness of semicrystalline thermoplastic elastomers when their crystallizable blocks hold a higher thermodynamic rigidity relative to noncrystallizable blocks. Our integrated approach paved the way for a better understanding of the structure-property relationship in thermoplastic elastomers.

Dynamic Monte Carlo simulations of strain-induced crystallization in multiblock copolymers: Effects of microphase separation

Semicrystalline multiblock copolymers holding alternatingly crystallizable and noncrystallizable blocks are good thermoplastic elastomers that are commonly processed through strain-induced crystallization. The crystalline microdomains play the role of physical crosslinks in the network of noncrystallizable blocks for high elasticity, and meanwhile their size diversity determines high toughness. We scheduled three integrated steps to study three physical effects of the coexisting noncrystallizable components, i.e. dilution, microphase separation and asymmetric block rigidity, on the size diversity of crystalline microdomains yielded by strain-induced crystallization in multiblock copolymers. We firstly considered the dilution effects in the extremely concentrated and diluted cases presumably generated by concentration fluctuations of crystallizable blocks, as responsible for the large-end and small-end crystalline microdomains, respectively. Our dynamic Monte Carlo simulations of strain-induced crystallization of the extremely concentrated and diluted crystallizable blocks in diblock and tetrablock copolymers demonstrated the dilution effects that the concentrated cases exhibit crystallization similar with bulk homopolymers, but the diluted cases make smaller crystalline microdomains than the cases without stretching, thus strain-induced crystallization in these two cases enhances the size diversity of crystalline microdomains (DOI: 10.1039/D2SM00193D). Hereby in the second step, we further compared the concentrated and diluted cases of strain-induced crystallization with and without microphase separation, and observed that microphase separation influences little to the concentrated cases, but makes more rather than smaller crystalline microdomains in the diluted cases, thus enhances their size diversity in a way different from the dilution effects. Higher extents of microphase separation will however weaken this enhancement. Our observations paved the way towards a better understanding of strain-induced crystallization in thermoplastic elastomers.

Aggregation-Induced Emission Poly(meth)acrylates for Photopatterning via Wavelength-Dependent Visible-Light-Regulated Controlled Radical Polymerization in Batch and Flow Conditions.

A robust wavelength-dependent visible-light-regulated reversible-deactivation radical polymerization protocol is first reported for the batch preparation of >20 aggregation-induced emission (AIE)-active polyacrylates and polymethacrylates. The resulting polymers possess narrow molar mass distributions (Đ ≈ 1.09-1.25) and high end-group fidelity at high monomer conversions (mostly >95%). This demonstrated control provides facile access to the in situ generation of complex sequence-defined tetrablock copolymers in one reactor, even while chain extending from less reactive monomers. Polymerizations can be successfully carried out under various irradiation conditions, including using UV, blue, green, and red LED light with more disperse polymers obtained at the longer, less energetic, wavelengths. We observe a red shift and wavelength dependence for the most efficient polymerization using LED illumination in a polymerization reaction. We find that the absorption of the copper(II) complex is not a reliable guide to reaction conditions. Moreover, the reported protocol is readily translated to a flow setup. The prepared AIE-active polymers are demonstrated to exhibit good photopatterning, making them promising materials for applications in advanced optoelectronic devices.

Ordering kinetics of a tapered copolymer based on isoprene and styrene.

High molar mass copolymers with a tapered interface are mechanically tough materials with an accessible order-to-disorder transition temperature and hence processability. We report the first ordering kinetics for a tapered tetrablock copolymer in comparison to a conventional diblock copolymer made sequentially. We show that tapered copolymers belong to the Brazovskii "universality class," where fluctuations play a dominant role. Consequently, the order-to-disorder transition has a very weak, fluctuation-induced first-order character. The ordering kinetics of the lamellar phase from the supercooled disordered melt revealed several distinct differences associated with the range of metastability (increased), the timescales (bimodal), and the exact mechanism of ordering. The results are discussed in terms of the reduced interaction parameter and the introduction of structural defects within the lamellar grains.

Core–Satellite Micelles by a Linear A1B1A2B2 Tetrablock Copolymer

Block copolymers in water or compatible solvents show micelles with various shapes, such as worm-like, vesicles, and spheres. In this study, we prepared core–satellite micelles by employing a polystyrene-block-polyisoprene-block-polystyrene-block-polyisoprene (S1I1S2I2) linear tetrablock copolymer. When a PS-compatible solvent, for example, dimethylacetamide or diethylphthalate, is used, the PI chains form the inside core, while the PS chains become a shell as long as the volume fraction of mid PI1 chains (fPI1) is large enough (0.2) to form a loop configuration, resulting in merging into spherical cores consisting of the PI2 chains. However, at smaller fPI1 (0.08), the short mid PI1 chains cannot merge into the PI2 core and therefore exist separately as small spherical micelles, which are referred to as the “satellite” micelles. Thus, the micelles consist of large central core spheres and smaller outside satellite spherical micelles.

Effect of polycaprolactone on physicochemical, biological, and mechanical properties of polyethylene oxide and polyamino acids nano block copolymers

AbstractThis work aims to design robust and biocompatible nano block‐copolymers (NBCPs) of polycaprolactone@‐polyethylene oxide‐polyaminoacid (PCL@‐PEO‐PAAs) by ring‐opening polymerization. Mechanical behavior including modulus, elongation at yield and break of the tetra block copolymer are studied at room temperature. The significant result lies when the extension at break is reduced by four times with an addition of 2 and 3 wt% of PCL respectively. The tensile strength at yield is found to be 22.39 ± 3.6 MPa, 34.66 ± 5.8 MPa, and 22.906 ± 4.1 MPa for 1, 2, and 3 wt% PCL@‐PEO‐PAAs NBCPs respectively. The partial hydrophobic nature of designed 3 wt% NBCP plays an important role in decreasing the strain at break and increasing the elongation at break of the composites compared to other 1 and 2 wt% NBCPs. In vitro cytotoxicity is observed to be more effective in irregular spheroid shaped 2 wt% compared to 1 and 3 wt% NBCPs due to a greater number of the amphiphilic groups present in the PCL grafted PEO‐PAAs nano BCPs. The ζ potential value for 3, 2, and 1 wt% NBCPs are found to be −26.9, −24.7, and − 15.8 MeV respectively due to higher electrostatic repulsion and became suitably used for in vivo applications.

Dynamic Monte Carlo simulations of strain-induced crystallization in multiblock copolymers: effects of dilution.

Multiblock copolymers containing alternating semicrystalline and molten blocks are good thermoplastic elastomers. Their crystallization in the stretching process is however complicated by the dilution effects, prior microphase separation and contrast chain rigidity of the molten blocks. We designed our systematic investigation with three integrated steps, and herein, as the first step, we considered only the dilution effects without prior microphase separation and contrast chain rigidity. We compared two extreme situations of local dilution separately corresponding to parallel-posited and antiparallel-posited block copolymers upon strain-induced crystallization. Our dynamic Monte Carlo simulations of diblock and tetrablock copolymers demonstrated that the stretching introduces a constraint on the diffusion of locally posited crystallizable blocks along the stretching direction for crystallization and thus enhances the dilution effects to result in a higher diversity in crystal stabilities. We observed that the strain-induced crystallization of parallel-posited copolymers behaved like the melt crystallization of homopolymers; in contrast, the strain-induced crystallization of antiparallel-posited copolymers yielded crystallites near the block junction, which are relatively small and less stable due to their local dilution suppressing their melting points. Similar to the case of spider dragline silks, two contrasting stabilities of crystallites in semicrystalline multiblock copolymers explain their good toughness. Our modeling approach paves the way toward a better understanding of the structure-property relationship in the semicrystalline thermoplastic elastomers.

ABC and ABAB Block Copolymers by Electrochemically Controlled Ring-Opening Polymerization.

An electrochemically controlled synthesis of multiblock copolymers by alternating the redox states of (salfan)Zr(OtBu)2 (salfan = 1,1'-di(2-tert-butyl-6-N-methylmethylenephenoxy)ferrocene) is reported. Aided by electrochemistry with a glassy carbon working electrode, an in situ potential switch alters the catalyst's oxidation state and its subsequent monomer (l-lactide, β-butyrolactone, or cyclohexene oxide) selectivity in one pot. Various multiblock copolymers were prepared, including an ABAB tetrablock copolymer, poly(cyclohexene oxide-b-lactide-b-cyclohexene oxide-b-lactide), and an ABC triblock copolymer, poly(hydroxybutyrate-b-cyclohexene oxide-b-lactide). The polymers produced using this technique are similar to those produced via a chemical redox reagent method, displaying moderately narrow dispersities (1.1-1.5) and molecular weights ranging from 7 to 26 kDa.

Pi-stacking Enhances Stability, Scalability of Formation, Control over Flexibility and Circulation Time of Polymeric Filaments.

Self-assembling filomicelles (FM) are of great interest to nanomedicine due to their structural flexibility, extensive systemic circulation time, and amenability to unique "cylinder-to-sphere" morphological transitions. However, current fabrication techniques for FM self-assembly are highly variable and difficult to scale. Here, we demonstrate that tetrablock copolymers composed of poly(ethylene glycol)-b-poly(propylene sulfide) (PEG-b-PPS) diblocks linked by a pi-stacking perylene bisimide (PBI) moiety permit rapid, scalable, and facile assembly of FM via the flash nanoprecipitation (FNP) method. Co-assembling the tetrablocks and PEG-b-PPS diblocks at different molar ratios resulted in mixed PBI-containing FM (mPBI-FM) with tunable length and flexibility. The flexibility of mPBI-FM can be optimized to decrease uptake by macrophages in vivo, leading to increased circulation time versus (-)PBI-FM without PBI tetrablocks after intravenous administration in mice. While PEG-b-PPS diblocks form FM within a narrow range of hydrophilic weight fractions, incorporation of pi-stacking PBI groups expanded this range to increase favorability of FM assembly. Furthermore, the aggregation-dependent fluorescence of PBI shifted during oxidation-induced "cylinder-to-sphere" transitions of mPBI-FM into micelles, resulting in a distinct emission wavelength for filamentous versus spherical nanostructures. Thus, incorporation of pi-stacking allows for rapid, scalable assembly of FM with tunable flexibility and stability for theranostic and nanomedicine applications.

Abstract 3107: HSB-1216, A Novel Agent for the Treatment of Chemotherapy-Resistant ES-SCLC

Abstract Small cell lung cancer (SCLC) is a highly malignant form of lung cancer that accounts for 15% of lung cancer cases. The tumor has a tendency to disseminate early resulting in ~ 85% patients being diagnosed with extensive stage disease (ES-SCLC). Chemotherapy has been the mainstay of treatment for many decades, until recently when immunotherapeutic agents have been approved as first-line agents. However, resistance to anti-cancer drugs represents the main cause of cancer-related deaths. Thus, new therapeutic approach to suppress chemotherapy-resistant ES-SCLC constitutes a significant unmet medical need. We have generated novel biodegradable QUATRAMERTM polymeric nanoparticles comprised of a polyethylene glycol (PEG)-polypropylene glycol (PPG)-PEG- polylactic acid (PLA)-tetra-block copolymer for the intracellular delivery of salinomycin (HSB-1216). Here we studied the HSB-1216 activity in a resistant SCLC cell line (NCI-H69AR). Compared to cisplatin and irinotecan, a second-line agent often used in ES-SCLC, HSB-1216 exhibited a ~7-fold and ~2-fold decrease in IC50in the aggressive and resistant variant of NCI-H69AR cell line and ~30-fold and ~18-fold decrease in a non-resistant NCI-H69 SCLC line. The tumorsphere formation assay has become an essential tool for quantifying cancer stem cells (CSC) and testing of anti-cancer agents. We used this assay to estimate an effect of HSB-1216 on NCI-H69AR tumorspheres .Our results demonstrated significant dose-dependent inhibition of tumorosphere formation in response to HSB-1216. In addition, exposure to HSB-1216 resulted in substantial decrease in number of CD44+/CD24- cells in comparison to untreated control. Furthermore, significant reduction in the expression of CSC markers such as ALDH1 and Oct3/Oct4 was seen when chemotherapy-resistant NCI-H69AR cells were treated with HSB-1216.Taken together, based on these findings, HSB-1216 is being developed as a novel agent in the treatment of second-line ES-SCLC in chemo-resistant tumors, where a gap exists in current standards of care. Further work of this novel agent is planned to outline its effect when combined with targeted and non-targeted therapies in both first- and third-line SCLC. Citation Format: Anees Mohammad, Sachchidanand Tiwari, Neha Mehrotra, Bozena Korczak, Steve Laumas, Sireesh Appajosyula, Harpal Singh, Surender M. Kharbanda. HSB-1216, A Novel Agent for the Treatment of Chemotherapy-Resistant ES-SCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 3107.

Cross-Linked Composite Gel Polymer Electrolyte Based on an H-Shaped Poly(ethylene oxide)-Poly(propylene oxide) Tetrablock Copolymer with SiO2 Nanoparticles for Solid-State Supercapacitor Applications.

Achieving high ionic conductivity, wide voltage window, and good mechanical strength in a single material remains a key challenge for polymer-based electrolytes for use in solid-state supercapacitors (SCs). Herein, we report cross-linked composite gel polymer electrolytes (CGPEs) based on multi-cross-linkable H-shaped poly(ethylene oxide)–poly(propylene oxide) (PEO-PPO) tetrablock copolymer precursors, SiO2 nanoparticles, and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, an ionic liquid (IL). Self-standing CGPE membranes with a high IL content were prepared using in situ cross-linking reactions between the silane groups present in the precursor and the SiO2 surface. The incorporation of an optimal amount of SiO2 increased the cross-linking density of the resulting CGPE while reducing polymer-chain ordering and, consequently, increasing both ionic conductivity and mechanical strength. As a result, the CGPE with 0.1 wt % SiO2 exhibited a high ionic conductivity (2.22 × 10–3 S cm–1 at 25 °C), good tensile strength (453 kPa), and high thermal stability up to 330 °C. Finally, an all-solid-state SC assembled with the prepared CGPE showed a high operating voltage (3 V), a large specific capacitance (103.9 F g–1 at 1 A g–1), and excellent durability (94% capacitance retention over 10,000 charge/discharge cycles), which highlights its strong potential as a solid-state electrolyte for SCs.

Enlarged Stable Phase Region of Hybrid Lamella-sphere Phase Enabled by A1B1A2(B2)m Branched Tetrablock Copolymer

Hybrid nanostructures possess a great potential for application in advanced nanotechnologies due to the anisotropic properties from different nanophases. Our previous work demonstrated that a linear A1B1A2B2 tetrablock copolymer of symmetric overall volume fraction can self-assemble into a hybrid lamella-sphere (LS) structure by tuning the relative length of the two A-blocks through self-consistent field theory (SCFT), where the spherical and the lamellar domains are mainly composed of the long A1- and short A2-blocks, respectively. However, the phase region of LS is limited. In order to expand the stable region of LS, we change the linear A1B1A2B2 copolymer to a branched A1B1A2(B2)m copolymer resulting in an increase of the local spontaneous curvature between A2- and B2-blocks. We examine the impact of the branching number m of B2-block on the stable region of LS in the phase diagram with respect to fA1 and XN for fixed fB=0.5 and fB1=0.26, and find that m=2 expands the LS region significantly in contrast to the linear architecture. On the other hand, the stability window of LS does not change notably when m=2 is increased to 3 in our calculated parameter space.

Frank-Kasper Phases Self-Assembled from a Linear A1B1A2B2 Tetrablock Copolymer.

The Frank-Kasper (FK) phases self-assembled from block copolymer systems have attracted abiding interest. In this work, the formation mechanism of the complex FK phases from the self-assembly of simple A1B1A2B2 tetrablock copolymers is investigated using self-consistent field theory (SCFT). For a typical set of parameter spaces, we utilize SCFT to construct a number of phase diagrams. In these phase diagrams, the FK phases exhibit a notable stability region. The stable region of the FK phases reveals that the distribution of A1 and A2 blocks can be precisely regulated by tuning the ratio of the A1/A2 block, wherein the long A1 blocks can aggregate within the "core" while the short A2 blocks can form the "shell" of a spherical domain in the FK phases, respectively, to accommodate the sizes and shapes of the spherical domains in the complex spherical packing phases. Besides, we also demonstrate that the existence of the B2 block plays a crucial factor to stabilize the FK phases.

Self-assembly of A1B1A2(B2)m branched tetrablock copolymer: Length scale and phase transition

In this paper, the self-assembly behaviors of branched A1B1A2(B2)m (m = 1, 2, 3) tetrablock copolymer with fixed χN = 80 and symmetric composition has been studied using the self-consistent field theory (SCFT), to reveal that the length ratio of B1-block plays a key role in stabilizing the hybrid lamella-sphere (LSA) phase as well as corresponding phase transitions. Specifically, we find that not only the stability regime but also the domain spacing of the LSA can be modulated through tuning the length of B1-block. So our results will provide helpful guidance for the experimental study on the hybrid nanostructures.

Merging of cationic RAFT and radical RAFT polymerizations with ring-opening polymerizations for the synthesis of asymmetric ABCD type tetrablock copolymers in one pot

A new bifunctional and switchable RAFT agent and a mechanism switching strategy were proposed to control the cationic RAFT polymerization, radical RAFT polymerization and ring-opening polymerization of vinyl and cyclic ester monomers and to produce block copolymers.

Self-organization of a 4-miktoarm star block copolymer induced by cylindrical confinement.

Self-consistent field calculations have been carried out to reveal the self-assembly behavior of a melt of the ABCD star tetrablock copolymer confined within a cylindrical nanopore. The miktoarm star block copolymer exhibits a rich self-assembly behavior with a myriad of interesting three-dimensional ordered phases with the potential to produce advanced nanomaterials. The broad array of ordered mesophases includes helical microstructures, stack of rings/doughnuts, honeycomb structure, and perforated lamella with beads, depending on the individual block fractions and the size of the cylindrical nanopore. Such chiral motifs generated from achiral polymeric molecules are fascinating due to their superior performance in sophisticated opto-electronic devices. The study also demonstrates an interesting morphology, viz. a honeycomb structure, obtained from the self-organization of ABCD star block copolymer molecules with equal block fractions. The system exhibits order-order phase transition covering a range of ordered morphologies by changing either the block fraction or the nanopore radius. A representative phase diagram in terms of block fractions is constructed. These novel ordered microstructures, arising mainly out of structural frustration and confinement-induced entropy loss, can serve as structural scaffolds to host the spatial distribution of nanoparticles resulting into novel nanocomposites with significantly enhanced as well as controllable properties.