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15 pages, 5829 KiB

Open AccessArticle

Disclosing Topographical and Chemical Patterns in Confined Films of High-Molecular-Weight Block Copolymers under Controlled Solvothermal Annealing

by Xiao Cheng, Jenny Tempeler, Serhiy Danylyuk, Alexander Böker and Larisa Tsarkova

Polymers 2024, 16(13), 1943; https://doi.org/10.3390/polym16131943 - 8 Jul 2024

Cited by 1 | Viewed by 2695

Abstract

The microphase separation of high-molecular-weight block copolymers into nanostructured films is strongly dependent on the surface fields. Both, the chain mobility and the effective interaction parameters can lead to deviations from the bulk morphologies in the structures adjacent to the substrate. Resolving frustrated [...] Read more.

The microphase separation of high-molecular-weight block copolymers into nanostructured films is strongly dependent on the surface fields. Both, the chain mobility and the effective interaction parameters can lead to deviations from the bulk morphologies in the structures adjacent to the substrate. Resolving frustrated morphologies with domain period L₀ above 100 nm is an experimental challenge. Here, solvothermal annealing was used to assess the contribution of elevated temperatures of the vapor T_v and of the substrate T_s on the evolution of the microphase-separated structures in thin films symmetric of polystyrene-b-poly(2vinylpyridine) block copolymer (PS-PVP) with L₀ about 120 nm. Pronounced topographic mesh-like and stripe patterns develop on a time scale of min and are attributed to the perforated lamella (PL) and up-standing lamella phases. By setting T_v/T_s combinations it is possible to tune the sizes of the resulting PL patterns by almost 10%. Resolving chemical periodicity using selective metallization of the structures revealed multiplication of the topographic stripes, i.e., complex segregation of the component within the topographic pattern, presumably as a result of morphological phase transition from initial non-equilibrium spherical morphology. Reported results reveal approaches to tune the topographical and chemical periodicity of microphase separation of high-molecular-weight block copolymers under strong confinement, which is essential for exploiting these structures as functional templates. Full article

(This article belongs to the Special Issue Block Copolymers: Synthesis, Self-Assembly and Application)

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14 pages, 3475 KiB

Open AccessArticle

Preparation and Characterization of Soft-Hard Block Copolymer of 3,4-IP-b-s-1,2-PBD Using a Robust Iron-Based Catalyst System

by Yingnan Zhao, Shiliang Xu, Yao Yu, Heng Liu, Feng Wang, Lihua Na, Qi Yang, Chunyu Zhang and Xuequan Zhang

Polymers 2024, 16(8), 1172; https://doi.org/10.3390/polym16081172 - 21 Apr 2024

Cited by 1 | Viewed by 1402

Abstract

A series of well-defined diblock copolymers, namely, 3,4-polyisoprene-block-syndiotactic-1,2-polybutadiene (3,4-PI-b-s-1,2-PBD), with a soft–hard block sequence were synthesized via an in situ sequential polymerization process using a robust iron-based catalytic system Fe(acac)₃/(isocyanoimino) triptenylphosphorane (IITP)/Alⁱ [...] Read more.

A series of well-defined diblock copolymers, namely, 3,4-polyisoprene-block-syndiotactic-1,2-polybutadiene (3,4-PI-b-s-1,2-PBD), with a soft–hard block sequence were synthesized via an in situ sequential polymerization process using a robust iron-based catalytic system Fe(acac)₃/(isocyanoimino) triptenylphosphorane (IITP)/AlⁱBu₃. This catalyst exhibits vigorous activity and temperature tolerance, achieving a polymerization activity of 5.41 × 10⁶ g mol_(Fe)⁻¹ h⁻¹ at 70 °C with a [IP]/[Fe] ratio of 15,000. Moreover, the quasi-living polymerization characteristics of the catalyst were verified through kinetic experiments. The first-stage polymerization of isoprene (IP) is performed at 30 °C to give a soft 3,4-PI block, and then a quantitative amount of 1,3-butadiene was added in situ to the quasi-living polymerization system to produce a second hard s-1,2-PBD. The s-1,2-PBD segments in block copolymers display a rodlike morphology contrasting with the spherulitic morphology characteristic of s-1,2-PBD homopolymers. The precise tunability of the length of the soft and hard chain segments of these novel elastic materials with the feed ratio of IP and BD, endowing them with outstanding mechanical properties and excellent dynamic mechanical properties, which are expected to be promising high-performance rubber materials. Full article

(This article belongs to the Special Issue Block Copolymers: Synthesis, Self-Assembly and Application)

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26 pages, 9023 KiB

Open AccessArticle

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

by Daniel T. Krause, Susanna Krämer, Vassilios Siozios, Andreas J. Butzelaar, Martin Dulle, Beate Förster, Patrick Theato, Joachim Mayer, Martin Winter, Stephan Förster, Hans-Dieter Wiemhöfer and Mariano Grünebaum

Polymers 2023, 15(9), 2128; https://doi.org/10.3390/polym15092128 - 29 Apr 2023

Cited by 2 | Viewed by 2078

Abstract

Poly(ethylene oxide) block copolymers (PEO_z 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 (PI_xPS_yPEO_z), a [...] Read more.

Poly(ethylene oxide) block copolymers (PEO_z 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 (PI_xPS_yPEO_z), a pronounced maximum ion conductivity was reported for short PEO_z molecular weights around 2 kg mol⁻¹. To later enable a systematic exploration of the influence of the PI_x and PS_y block lengths and related morphologies on the ion conductivity, a synthetic method is needed where the short PEO_z block length can be kept constant, while the PI_x and PS_y 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 PEO_z chains to terminate PI_xPS_y BCPs. The attachment proceeds to full conversion in a simplified and reproducible one-pot polymerization such that PI_xPS_yPEO_z with narrow chain length distribution and a fixed PEO_z block length of z = 1.9 kg mol⁻¹ and a Đ = 1.03 are obtained. The successful quantitative end group modification of the PEO_z 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 PEO_z BCP system is ideally suitable to relate BCP morphology, order and orientation to macroscopic Li⁺ conductivity in Li⁺ batteries. Full article

(This article belongs to the Special Issue Block Copolymers: Synthesis, Self-Assembly and Application)

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15 pages, 3701 KiB

Open AccessArticle

Non-Bulk Morphologies of Extremely Thin Block Copolymer Films Cast on Topographically Defined Substrates Featuring Deep Trenches: The Importance of Lateral Confinement

by Elisheva Michman, Meirav Oded and Roy Shenhar

Polymers 2023, 15(4), 1035; https://doi.org/10.3390/polym15041035 - 19 Feb 2023

Cited by 2 | Viewed by 1803

Abstract

Directed self-assembly of block copolymers is evolving toward applications that are more defect-tolerant but still require high morphological control and could benefit from simple, inexpensive fabrication processes. Previously, we demonstrated that simply casting ultra-thin block copolymer films on topographically defined substrates leads to [...] Read more.

Directed self-assembly of block copolymers is evolving toward applications that are more defect-tolerant but still require high morphological control and could benefit from simple, inexpensive fabrication processes. Previously, we demonstrated that simply casting ultra-thin block copolymer films on topographically defined substrates leads to hierarchical structures with dual patterns in a controlled manner and unraveled the dependence of the local morphology on the topographic feature dimensions. In this article, we discuss the extreme of the ultraconfined thickness regime at the border of film dewetting. Additional non-bulk morphologies are observed at this extreme, which further elaborate the arsenal of dual patterns that could be obtained in coexistence with full placement control. It is shown that as the thickness confinement approaches its limit, lateral confinement imposed by the width of the plateaus becomes a critical factor influencing the local morphology. Full article

(This article belongs to the Special Issue Block Copolymers: Synthesis, Self-Assembly and Application)

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12 pages, 2948 KiB

Open AccessArticle

Facile Preparation of Cobalt Nanoparticles Encapsulated Nitrogen-Doped Carbon Sponge for Efficient Oxygen Reduction Reaction

by Ying Leng, Kai Jin, Tian Wang and Hui Sun

Polymers 2023, 15(3), 521; https://doi.org/10.3390/polym15030521 - 19 Jan 2023

Cited by 4 | Viewed by 1943

Abstract

The facile preparation of non-noble metal nanoparticle loaded carbon nanomaterials is promising for efficient oxygen reduction reaction (ORR) electrocatalysis. Herein, a facile preparation strategy is proposed to prepare nitrogen-doped carbon sponge loaded with fine cobalt nanoparticles by the direct pyrolysis of the cobalt [...] Read more.

The facile preparation of non-noble metal nanoparticle loaded carbon nanomaterials is promising for efficient oxygen reduction reaction (ORR) electrocatalysis. Herein, a facile preparation strategy is proposed to prepare nitrogen-doped carbon sponge loaded with fine cobalt nanoparticles by the direct pyrolysis of the cobalt ions adsorbed polymeric precursor. The polymeric sponge precursor with continuous framework and high porosity is formed by the self-assembly of a poly(amic acid). Taking advantage of the negatively charged surface and porous structure, cobalt ions can be efficiently adsorbed into the polymeric sponge. After pyrolysis, fine cobalt nanoparticles covered by carbon layers are formed, while the sponge-like structure of the precursor is also well-preserved in order to give cobalt nanoparticles loaded nitrogen-doped carbon sponges (Co/CoO@NCS) with a high loading content of 44%. The Co/CoO@NCS exhibits promising catalytic activity toward ORR with a half-wave potential of 0.830 V and a limiting current density of 4.71 mA cm⁻². Overall, we propose a facile polymer self-assembly strategy to encapsulate transition metal nanoparticles with high loading content on a nitrogen-doped carbon sponge for efficient ORR catalysis. Full article

(This article belongs to the Special Issue Block Copolymers: Synthesis, Self-Assembly and Application)

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16 pages, 4639 KiB

Open AccessArticle

Dynamic Light Scattering Based Microrheology of End-Functionalised Triblock Copolymer Solutions

by Ren Liu, Alessio Caciagli, Jiaming Yu, Xiaoying Tang, Rini Ghosh and Erika Eiser

Polymers 2023, 15(3), 481; https://doi.org/10.3390/polym15030481 - 17 Jan 2023

Cited by 1 | Viewed by 2440

Abstract

Nano-sized particles functionalised with short single-stranded (ss)DNAs can act as detectors of complementary DNA strands. Here we consider tri-block-copolymer-based, self-assembling DNA-coated nanoparticles. The copolymers are chemically linked to the DNA strands via azide (N

_{3}

) groups. The micelles aggregate when they are [...] Read more.

Nano-sized particles functionalised with short single-stranded (ss)DNAs can act as detectors of complementary DNA strands. Here we consider tri-block-copolymer-based, self-assembling DNA-coated nanoparticles. The copolymers are chemically linked to the DNA strands via azide (N

_{3}

) groups. The micelles aggregate when they are linked with complementary ssDNA. The advantage of such block-copolymer-based systems is that they are easy to make. Here we show that DNA functionalisation results in inter-micellar attraction, but that N

_{3}

-groups that have not reacted with the DNA detector strands also change the phase behaviour of the tri-block polymer solution. We studied the triblock copolymer, Pluronic^® F108, which forms spherical micelles in aqueous solutions upon heating. We find that the triblock chains ending with either an N

_{3}

or N

_{3}

-DNA complex show a dramatic change in phase behaviour. In particular, the N

_{3}

-functionalisation causes the chain ends to cluster below the critical micelle temperature (CMT) of pure F108, forming flower-micelles with the N

_{3}

-groups at the core, while the PPO groups are exposed to the solvent. Above the CMT, we see an inversion with the PPO chains forming the micellar core, while the N

_{3}

-groups are now aggregating on the periphery, inducing an attraction between the micelles. Our results demonstrate that, due to the two competing self-assembling mechanisms, the system can form transient hydrogels. Full article

(This article belongs to the Special Issue Block Copolymers: Synthesis, Self-Assembly and Application)

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Review

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15 pages, 9036 KiB

Open AccessReview

Substrate Neutrality for Obtaining Block Copolymer Vertical Orientation

by Kaitlyn Hillery, Nayanathara Hendeniya, Shaghayegh Abtahi, Caden Chittick and Boyce Chang

Polymers 2024, 16(12), 1740; https://doi.org/10.3390/polym16121740 - 19 Jun 2024

Viewed by 856

Abstract

Nanopatterning methods utilizing block copolymer (BCP) self-assembly are attractive for semiconductor fabrication due to their molecular precision and high resolution. Grafted polymer brushes play a crucial role in providing a neutral surface conducive for the orientational control of BCPs. These brushes create a [...] Read more.

Nanopatterning methods utilizing block copolymer (BCP) self-assembly are attractive for semiconductor fabrication due to their molecular precision and high resolution. Grafted polymer brushes play a crucial role in providing a neutral surface conducive for the orientational control of BCPs. These brushes create a non-preferential substrate, allowing wetting of the distinct chemistries from each block of the BCP. This vertically aligns the BCP self-assembled lattice to create patterns that are useful for semiconductor nanofabrication. In this review, we aim to explore various methods used to tune the substrate and BCP interface toward a neutral template. This review takes a historical perspective on the polymer brush methods developed to achieve substrate neutrality. We divide the approaches into copolymer and blended homopolymer methods. Early attempts to obtain neutral substrates utilized end-grafted random copolymers that consisted of monomers from each block. This evolved into side-group-grafted chains, cross-linked mats, and block cooligomer brushes. Amidst the augmentation of the chain architecture, homopolymer blends were developed as a facile method where polymer chains with each chemistry were mixed and grafted onto the substrate. This was largely believed to be challenging due to the macrophase separation of the chemically incompatible chains. However, innovative methods such as sequential grafting and BCP compatibilizers were utilized to circumvent this problem. The advantages and challenges of each method are discussed in the context of neutrality and feasibility. Full article

(This article belongs to the Special Issue Block Copolymers: Synthesis, Self-Assembly and Application)

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24 pages, 3337 KiB

Open AccessReview

Processive Pathways to Metastability in Block Copolymer Thin Films

by Nayanathara Hendeniya, Kaitlyn Hillery and Boyce S. Chang

Polymers 2023, 15(3), 498; https://doi.org/10.3390/polym15030498 - 18 Jan 2023

Cited by 2 | Viewed by 2513

Abstract

Block copolymers (BCPs) self-assemble into intricate nanostructures that enhance a multitude of advanced applications in semiconductor processing, membrane science, nanopatterned coatings, nanocomposites, and battery research. Kinetics and thermodynamics of self-assembly are crucial considerations in controlling the nanostructure of BCP thin films. The equilibrium [...] Read more.

Block copolymers (BCPs) self-assemble into intricate nanostructures that enhance a multitude of advanced applications in semiconductor processing, membrane science, nanopatterned coatings, nanocomposites, and battery research. Kinetics and thermodynamics of self-assembly are crucial considerations in controlling the nanostructure of BCP thin films. The equilibrium structure is governed by a molecular architecture and the chemistry of its repeat units. An enormous library of materials has been synthesized and they naturally produce a rich equilibrium phase diagram. Non-equilibrium phases could potentially broaden the structural diversity of BCPs and relax the synthetic burden of creating new molecules. Furthermore, the reliance on synthesis could be complicated by the scalability and the materials compatibility. Non-equilibrium phases in BCPs, however, are less explored, likely due to the challenges in stabilizing the metastable structures. Over the past few decades, a variety of processing techniques were introduced that influence the phase transformation of BCPs to achieve a wide range of morphologies. Nonetheless, there is a knowledge gap on how different processive pathways can induce and control the non-equilibrium phases in BCP thin films. In this review, we focus on different solvent-induced and thermally induced processive pathways, and their potential to control the non-equilibrium phases with regards to their unique aspects and advantages. Furthermore, we elucidate the limitations of these pathways and discuss the potential avenues for future investigations. Full article

(This article belongs to the Special Issue Block Copolymers: Synthesis, Self-Assembly and Application)

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