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Block Copolymers with Crystallizable Blocks: Synthesis, Self-Assembly and Applications

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A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Analysis and Characterization".

Deadline for manuscript submissions: closed (31 October 2021) | Viewed by 28795

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Dr. Holger Schmalz

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Guest Editor

1. Macromolecular Chemistry II, University of Bayreuth, 95440 Bayreuth, Germany
2. Keylab Synthesis and Molecular Characterization, Bavarian Polymer Institute, University of Bayreuth, 95440 Bayreuth, Germany
Interests: Living and controlled polymerization techniques, block copolymer synthesis, crystallization driven self-assembly, Janus and patchy particles, mesostructured templates for heterogenous catalysis, Raman imaging of complex mesostructured polymer systems

Prof. Dr. Volker Abetz

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Guest Editor

1. Institute of Physical Chemistry, Universität Hamburg, Grindelallee 117, 20146 Hamburg, Germany
2. Institute of Membrane Research, Helmholtz-Zentrum Hereon, Max-Planck-Straße 1, 21502 Geesthacht, Germany
Interests: self-assembly; block copolymers; polymer blends; nanocomposites; supramolecular polymers; membranes; controlled polymerizations
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Special Issue Information

Dear Colleagues,

Block copolymers with crystallizable blocks have recently moved to the forefront of current research owing to their unique self-assembly behaviour and properties. New synthetic concepts give, for example, access to tetrablock copolymers with four crystalline blocks, bio-based thermoplastic elastomers (e.g., based on ABA triblock copolymers with hard poly(L-lactide) (PLLA) segments), and conjugated semi-crystalline block copolymers for photovoltaics and allow for new, exciting insights into the interplay between the microphase separation and crystallization controlling self-assembly in bulk (confined vs. break-out crystallization).

Concerning self-assembly in solution, the pioneering work of Manners and Winnik paved the way to a myriad of crystalline-core micellar structures and hierarchical superstructures that were not accessible before via self-assembly of fully amorphous block copolymers. In analogy to living polymerization, crystallization-driven self-assembly (CDSA) can be conducted in a living manner using small micellar fragments as seeds for the addition of unimers (molecularly dissolved block copolymers bearing a crystallizable block). This allows for the production of cylindrical micelles with defined length, length distribution, corona chemistries (block type or patchy corona), branched micelles, and micellar superstructures (e.g., two-dimensional (2D) lenticular platelets, scarf-shaped micelles, multidimensional micellar assemblies, and cross and “windmill”-like supermicelles). Moreover, amphiphilic crystalline-core micelles based on PLLA or corresponding stereo-complexes (e.g., PLLA/PDLA (poly(D-lactide)) show interesting potential for biomedical applications (controlled release and delivery of drugs). Use of the process termed polymerization-induced crystallization-driven self-assembly (PI-CDSA) enables the one-pot production of a highly concentrated dispersion of crystalline-core cylindrical micelles.

This Special Issue aims to present a collection of articles describing new developments in the synthesis and self-assembly (bulk and solution) of block copolymers with crystallizable blocks. It also aims to address emerging applications for these exciting materials.

Dr. Holger Schmalz
Guest Editor

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Keywords

block copolymer,
semi-crystalline,
self-assembly,
crystallization driven self-assembly,
bulk morphologies,
hierarchical superstructures,
biobased polymers

Published Papers (11 papers)

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Editorial

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5 pages, 223 KiB

Open AccessEditorial

Block Copolymers with Crystallizable Blocks: Synthesis, Self-Assembly and Applications

by Holger Schmalz and Volker Abetz

Polymers 2022, 14(4), 696; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14040696 - 11 Feb 2022

Cited by 3 | Viewed by 1787

Abstract

Block copolymers with crystallizable blocks are a highly interesting class of materials owing to their unique self-assembly behaviour both in bulk and solution. This Special Issue brings together new developments in the synthesis and self-assembly of semicrystalline block copolymers and also addresses potential [...] Read more.

(This article belongs to the Special Issue Block Copolymers with Crystallizable Blocks: Synthesis, Self-Assembly and Applications)

Research

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14 pages, 5299 KiB

Open AccessArticle

Morphology and Degradation of Multicompartment Microparticles Based on Semi-Crystalline Polystyrene-block-Polybutadiene-block-Poly(L-lactide) Triblock Terpolymers

by Nicole Janoszka, Suna Azhdari, Christian Hils, Deniz Coban, Holger Schmalz and André H. Gröschel

Polymers 2021, 13(24), 4358; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13244358 - 13 Dec 2021

Cited by 3 | Viewed by 2431

Abstract

The confinement assembly of block copolymers shows great potential regarding the formation of functional microparticles with compartmentalized structure. Although a large variety of block chemistries have already been used, less is known about microdomain degradation, which could lead to mesoporous microparticles with particularly complex morphologies for ABC triblock terpolymers. Here, we report on the formation of triblock terpolymer-based, multicompartment microparticles (MMs) and the selective degradation of domains into mesoporous microparticles. A series of polystyrene-block-polybutadiene-block-poly(L-lactide) (PS-b-PB-b-PLLA, SBL) triblock terpolymers was synthesized by a combination of anionic vinyl and ring-opening polymerization, which were transformed into microparticles through evaporation-induced confinement assembly. Despite different block compositions and the presence of a crystallizable PLLA block, we mainly identified hexagonally packed cylinders with a PLLA core and PB shell embedded in a PS matrix. Emulsions were prepared with Shirasu Porous Glass (SPG) membranes leading to a narrow size distribution of the microparticles and control of the average particle diameter, d ≈ 0.4 µm–1.8 µm. The core–shell cylinders lie parallel to the surface for particle diameters d < 0.5 µm and progressively more perpendicular for larger particles d > 0.8 µm as verified with scanning and transmission electron microscopy and particle cross-sections. Finally, the selective degradation of the PLLA cylinders under basic conditions resulted in mesoporous microparticles with a pronounced surface roughness. Full article

(This article belongs to the Special Issue Block Copolymers with Crystallizable Blocks: Synthesis, Self-Assembly and Applications)

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14 pages, 2734 KiB

Open AccessArticle

Membrane Separation of Gaseous Hydrocarbons by Semicrystalline Multiblock Copolymers: Role of Cohesive Energy Density and Crystallites of the Polyether Block

by Md. Mushfequr Rahman

Polymers 2021, 13(23), 4181; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13234181 - 29 Nov 2021

Cited by 4 | Viewed by 1946

Abstract

The energy-efficient separation of hydrocarbons is critically important for petrochemical industries. As polymeric membranes are ideal candidates for such separation, it is essential to explore the fundamental relationships between the hydrocarbon permeation mechanism and the physical properties of the polymers. In this study, the permeation mechanisms of methane, ethane, ethene, propane, propene and n-butane through three commercial multiblock copolymers PEBAX 2533, PolyActive1500PEGT77PBT23 and PolyActive4000PEGT77PBT23 are thoroughly investigated at 33 °C. This study aims to investigate the influence of cohesive energy density and crystallites of the polyether block of multiblock copolymers on hydrocarbon separation. The hydrocarbon separation behavior of the polymers is explained based on the solution–diffusion model, which is commonly accepted for gas permeation through nonporous polymeric membrane materials. Full article

(This article belongs to the Special Issue Block Copolymers with Crystallizable Blocks: Synthesis, Self-Assembly and Applications)

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25 pages, 9453 KiB

Open AccessArticle

Crystallization and Morphology of Triple Crystalline Polyethylene-b-poly(ethylene oxide)-b-poly(ε-caprolactone) PE-b-PEO-b-PCL Triblock Terpolymers

by Eider Matxinandiarena, Agurtzane Múgica, Manuela Zubitur, Viko Ladelta, George Zapsas, Dario Cavallo, Nikos Hadjichristidis and Alejandro J. Müller

Polymers 2021, 13(18), 3133; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13183133 - 16 Sep 2021

Cited by 4 | Viewed by 2338

Abstract

The morphology and crystallization behavior of two triblock terpolymers of polymethylene, equivalent to polyethylene (PE), poly (ethylene oxide) (PEO), and poly (ε-caprolactone) (PCL) are studied: PE₂₂^7.1-b-PEO₄₆^15.1-b-PCL₃₂^10.4 (T1) and PE₃₇^9.5-b-PEO₃₄^8.8-b-PCL₂₉^7.6 (T2) (superscripts give number average molecular weights in kg/mol and subscripts composition in wt %). The three blocks are potentially crystallizable, and the triple crystalline nature of the samples is investigated. Polyhomologation (C1 polymerization), ring-opening polymerization, and catalyst-switch strategies were combined to synthesize the triblock terpolymers. In addition, the corresponding PE-b-PEO diblock copolymers and PE homopolymers were also analyzed. The crystallization sequence of the blocks was determined via three independent but complementary techniques: differential scanning calorimetry (DSC), in situ SAXS/WAXS (small angle X-ray scattering/wide angle X-ray scattering), and polarized light optical microscopy (PLOM). The two terpolymers (T1 and T2) are weakly phase segregated in the melt according to SAXS. DSC and WAXS results demonstrate that in both triblock terpolymers the crystallization process starts with the PE block, continues with the PCL block, and ends with the PEO block. Hence triple crystalline materials are obtained. The crystallization of the PCL and the PEO block is coincident (i.e., it overlaps); however, WAXS and PLOM experiments can identify both transitions. In addition, PLOM shows a spherulitic morphology for the PE homopolymer and the T1 precursor diblock copolymer, while the other systems appear as non-spherulitic or microspherulitic at the last stage of the crystallization process. The complicated crystallization of tricrystalline triblock terpolymers can only be fully grasped when DSC, WAXS, and PLOM experiments are combined. This knowledge is fundamental to tailor the properties of these complex but fascinating materials. Full article

(This article belongs to the Special Issue Block Copolymers with Crystallizable Blocks: Synthesis, Self-Assembly and Applications)

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17 pages, 2658 KiB

Open AccessArticle

In-Depth Analysis of the Effect of Fragmentation on the Crystallization-Driven Self-Assembly Growth Kinetics of 1D Micelles Studied by Seed Trapping

by Gerald Guerin, Paul A. Rupar and Mitchell A. Winnik

Polymers 2021, 13(18), 3122; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13183122 - 16 Sep 2021

Cited by 2 | Viewed by 1846

Abstract

Studying the growth of 1D structures formed by the self-assembly of crystalline-coil block copolymers in solution at elevated temperatures is a challenging task. Like most 1D fibril structures, they fragment and dissolve when the solution is heated, creating a mixture of surviving crystallites and free polymer chains. However, unlike protein fibrils, no new nuclei are formed upon cooling and only the surviving crystallites regrow. Here, we report how trapping these crystallites at elevated temperatures allowed us to study their growth kinetics at different annealing times and for different amounts of unimer added. We developed a model describing the growth kinetics of these crystallites that accounts for fragmentation accompanying the 1D growth process. We show that the growth kinetics follow a stretched exponential law that may be due to polymer fractionation. In addition, by evaluating the micelle growth rate as a function of the concentration of unimer present in solution, we could conclude that the micelle growth occurred in the mononucleation regime. Full article

(This article belongs to the Special Issue Block Copolymers with Crystallizable Blocks: Synthesis, Self-Assembly and Applications)

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14 pages, 4151 KiB

Open AccessArticle

Double Crystallization and Phase Separation in Polyethylene—Syndiotactic Polypropylene Di-Block Copolymers

by Claudio De Rosa, Rocco Di Girolamo, Alessandra Cicolella, Giovanni Talarico and Miriam Scoti

Polymers 2021, 13(16), 2589; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13162589 - 04 Aug 2021

Cited by 8 | Viewed by 2179

Abstract

Crystallization and phase separation in the melt in semicrystalline block copolymers (BCPs) compete in defining the final solid state structure and morphology. In crystalline–crystalline di-block copolymers the sequence of crystallization of the two blocks plays a definitive role. In this work we show that the use of epitaxial crystallization on selected crystalline substrates allows achieving of a control over the crystallization of the blocks by inducing crystal orientations of the different crystalline phases and a final control over the global morphology. A sample of polyethylene-block-syndiotactic polypropylene (PE-b-sPP) block copolymers has been synthesized with a stereoselective living organometallic catalyst and epitaxially crystallized onto crystals of two different crystalline substrates, p-terphenyl (3Ph) and benzoic acid (BA). The epitaxial crystallization on both substrates produces formation of highly ordered morphologies with crystalline lamellae of sPP and PE highly oriented along one direction. However, the epitaxial crystallization onto 3Ph should generate a single orientation of sPP crystalline lamellae highly aligned along one direction and a double orientation of PE lamellae, whereas BA crystals should induce high orientation of only PE crystalline lamellae. Thanks to the use of the two selective substrates, the final morphology reveals the sequence of crystallization events during cooling from the melt and what is the dominant event that drives the final morphology. The observed single orientation of both crystalline PE and sPP phases on both substrates, indeed, indicates that sPP crystallizes first onto 3Ph defining the overall morphology and PE crystallizes after sPP in the confined interlamellar sPP regions. Instead, PE crystallizes first onto BA defining the overall morphology and sPP crystallizes after PE in the confined interlamellar PE regions. This allows for discriminating between the different crystalline phases and defining the final morphology, which depends on which polymer block crystallizes first on the substrate. This work also shows that the use of epitaxial crystallization and the choice of suitable substrate offer a means to produce oriented nanostructures and morphologies of block copolymers depending on the composition and the substrates. Full article

(This article belongs to the Special Issue Block Copolymers with Crystallizable Blocks: Synthesis, Self-Assembly and Applications)

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27 pages, 3869 KiB

Open AccessArticle

Phase Transitions in Poly(vinylidene fluoride)/Polymethylene-Based Diblock Copolymers and Blends

by Nicolás María, Jon Maiz, Daniel E. Martínez-Tong, Angel Alegria, Fatimah Algarni, George Zapzas, Nikos Hadjichristidis and Alejandro J. Müller

Polymers 2021, 13(15), 2442; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13152442 - 24 Jul 2021

Cited by 8 | Viewed by 3100

Abstract

The crystallization and morphology of two linear diblock copolymers based on polymethylene (PM) and poly(vinylidene fluoride) (PVDF) with compositions PM₂₃-b-PVDF₇₇ and PM₃₈-b-PVDF₆₂ (where the subscripts indicate the relative compositions in wt%) were compared with blends of neat components with identical compositions. The samples were studied by SAXS (Small Angle X-ray Scattering), WAXS (Wide Angle X-ray Scattering), PLOM (Polarized Light Optical Microscopy), TEM (Transmission Electron Microscopy), DSC (Differential Scanning Calorimetry), BDS (broadband dielectric spectroscopy), and FTIR (Fourier Transform Infrared Spectroscopy). The results showed that the blends are immiscible, while the diblock copolymers are miscible in the melt state (or very weakly segregated). The PVDF component crystallization was studied in detail. It was found that the polymorphic structure of PVDF was a strong function of its environment. The number of polymorphs and their amount depended on whether it was on its own as a homopolymer, as a block component in the diblock copolymers or as an immiscible phase in the blends. The cooling rate in non-isothermal crystallization or the crystallization temperature in isothermal tests also induced different polymorphic compositions in the PVDF crystals. As a result, we were able to produce samples with exclusive ferroelectric phases at specific preparation conditions, while others with mixtures of paraelectric and ferroelectric phases. Full article

(This article belongs to the Special Issue Block Copolymers with Crystallizable Blocks: Synthesis, Self-Assembly and Applications)

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12 pages, 2087 KiB

Open AccessArticle

Precise Tuning of Polymeric Fiber Dimensions to Enhance the Mechanical Properties of Alginate Hydrogel Matrices

by Zehua Li, Amanda K. Pearce, Andrew P. Dove and Rachel K. O’Reilly

Polymers 2021, 13(13), 2202; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13132202 - 02 Jul 2021

Cited by 10 | Viewed by 2731

Abstract

Hydrogels based on biopolymers, such as alginate, are commonly used as scaffolds in tissue engineering applications as they mimic the features of the native extracellular matrix (ECM). However, in their native state, they suffer from drawbacks including poor mechanical performance and a lack of biological functionalities. Herein, we have exploited a crystallization-driven self-assembly (CDSA) methodology to prepare well-defined one-dimensional micellar structures with controlled lengths to act as a mimic of fibrillar collagen in native ECM and improve the mechanical strength of alginate-based hydrogels. Poly(ε-caprolactone)-b-poly(methyl methacrylate)-b-poly(N, N-dimethyl acrylamide) triblock copolymers were self-assembled into 1D cylindrical micelles with precise lengths using CDSA epitaxial growth and subsequently combined with calcium alginate hydrogel networks to obtain nanocomposites. Rheological characterization determined that the inclusion of the cylindrical structures within the hydrogel network increased the strength of the hydrogel under shear. Furthermore, the strain at flow point of the alginate-based hydrogel was found to increase with nanoparticle content, reaching an improvement of 37% when loaded with 500 nm cylindrical micelles. Overall, this study has demonstrated that one-dimensional cylindrical nanoparticles with controlled lengths formed through CDSA are promising fibrillar collagen mimics to build ECM scaffold models, allowing exploration of the relationship between collagen fiber size and matrix mechanical properties. Full article

(This article belongs to the Special Issue Block Copolymers with Crystallizable Blocks: Synthesis, Self-Assembly and Applications)

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10 pages, 29229 KiB

Open AccessArticle

Self-Seeding Procedure for Obtaining Stacked Block Copolymer Lamellar Crystals in Solution

by Brahim Bessif, Thomas Pfohl and Günter Reiter

Polymers 2021, 13(11), 1676; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13111676 - 21 May 2021

Cited by 5 | Viewed by 1843

Abstract

We examined the formation of self-seeded platelet-like crystals from polystyrene-block-polyethylene oxide (PS-b-PEO) diblock copolymers in toluene as a function of polymer concentration (

c

), crystallization temperature (

T_{C}

), and self-seeding temperature (

T_{SS}

). We [...] Read more.

We examined the formation of self-seeded platelet-like crystals from polystyrene-block-polyethylene oxide (PS-b-PEO) diblock copolymers in toluene as a function of polymer concentration (

c

), crystallization temperature (

T_{C}

), and self-seeding temperature (

T_{SS}

). We showed that the number (

N

) of platelet-like crystals and their mean lateral size (

L

) can be controlled through a self-seeding procedure. As (homogeneous) nucleation was circumvented by the self-seeding procedure,

N

did not depend on

T_{C}

N

increased linearly with

c

and decayed exponentially with

T_{SS}

but was not affected significantly by the time the sample was kept at

T_{SS}

. The solubility limit of PS-b-PEO in toluene (

c

*), which was derived from the linear extrapolation of

N (c)

\to

0 and from the total deposited mass of the platelets per area

(M_{C} (c) \to 0

), depended on

T_{C}

. We have also demonstrated that at low

N

, stacks consisting of a (large) number (

η

) of uniquely oriented lamellae can be achieved. At a given

T_{C}

L

was controlled by

N

and

η

as well as by

∆ c = c - c^{*}

. Thus, besides being able to predict size and number of platelet-like crystals, the self-seeding procedure also allowed control of the number of stacked lamellae in these crystals. Full article

(This article belongs to the Special Issue Block Copolymers with Crystallizable Blocks: Synthesis, Self-Assembly and Applications)

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Review

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23 pages, 3982 KiB

Open AccessReview

Solution Self-Assembly of Coil-Crystalline Diblock Copolypeptoids Bearing Alkyl Side Chains

by Naisheng Jiang and Donghui Zhang

Polymers 2021, 13(18), 3131; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13183131 - 16 Sep 2021

Cited by 11 | Viewed by 2582

Abstract

Polypeptoids, a class of synthetic peptidomimetic polymers, have attracted increasing attention due to their potential for biotechnological applications, such as drug/gene delivery, sensing and molecular recognition. Recent investigations on the solution self-assembly of amphiphilic block copolypeptoids highlighted their capability to form a variety of nanostructures with tailorable morphologies and functionalities. Here, we review our recent findings on the solutions self-assembly of coil-crystalline diblock copolypeptoids bearing alkyl side chains. We highlight the solution self-assembly pathways of these polypeptoid block copolymers and show how molecular packing and crystallization of these building blocks affect the self-assembly behavior, resulting in one-dimensional (1D), two-dimensional (2D) and multidimensional hierarchical polymeric nanostructures in solution. Full article

(This article belongs to the Special Issue Block Copolymers with Crystallizable Blocks: Synthesis, Self-Assembly and Applications)

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26 pages, 3456 KiB

Open AccessReview

Patchy Micelles with a Crystalline Core: Self-Assembly Concepts, Properties, and Applications

by Christian Hils, Ian Manners, Judith Schöbel and Holger Schmalz

Polymers 2021, 13(9), 1481; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13091481 - 04 May 2021

Cited by 21 | Viewed by 4077

Abstract

Crystallization-driven self-assembly (CDSA) of block copolymers bearing one crystallizable block has emerged to be a powerful and highly relevant method for the production of one- and two-dimensional micellar assemblies with controlled length, shape, and corona chemistries. This gives access to a multitude of potential applications, from hierarchical self-assembly to complex superstructures, catalysis, sensing, nanomedicine, nanoelectronics, and surface functionalization. Related to these applications, patchy crystalline-core micelles, with their unique, nanometer-sized, alternating corona segmentation, are highly interesting, as this feature provides striking advantages concerning interfacial activity, functionalization, and confinement effects. Hence, this review aims to provide an overview of the current state of the art with respect to self-assembly concepts, properties, and applications of patchy micelles with crystalline cores formed by CDSA. We have also included a more general discussion on the CDSA process and highlight block-type co-micelles as a special type of patchy micelle, due to similarities of the corona structure if the size of the blocks is well below 100 nm. Full article

(This article belongs to the Special Issue Block Copolymers with Crystallizable Blocks: Synthesis, Self-Assembly and Applications)

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