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Phase Behavior in Polymers

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

Deadline for manuscript submissions: closed (30 April 2018) | Viewed by 57736

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Prof. Dr. Eamor M. Woo

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Department of Chemical Engineering, National Cheng Kung University, No. 1, University Road, Tainan 701-01, Taiwan
Interests: polymer crystallization and morphology; self-assembly; photonic crystals; biodegradable polymers; nanocomposites
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Special Issue Information

Dear Colleagues,

Polymers are made of repeating units—monomers of variety of structures. Thus, architects of polymer strutures influence the phase behavior in many aspects. Polymers of different structures (variations in monomer types, Mw, copolymerization, branching, crosslinking, etc.) can display phase behavior in many ways. Furthermore, polymers can be blended/mixed with other polymers or low-Mw compounds or solvents to display even wider and complex myriads of phase behavior. The phase behavior of polymers, in turn, can influence the physical and mechanical properties for ultimate applications. In wider scopes, polymers with semicrystalline structures contain at least two phases: The crystalline and amorphous domains, and their crystal-assembled morphologies also determine their applications. Although fundamentals of polymer phase behavior in polymers, blends and block copolymers has been long widely studied, well understood, and soundly established in past few decades, recent significant advances in polymer self-assembly, supramolecular architects, photonics, biomemetics and biomedical fields, etc., demand a more timely Special Issue.

This Special Issue, “Phase Behavior in Polymers”, aims to be a collection of high-caliber original/review papers focusing on recent progresses on: (a) polymer crystal-amorphous phases in bulks or thin films; (b) binary-ternary homopolymer mixtures/blends and diblock/triblock copolymers exhibiting macrophase/microphase separation and phase-domain morphology; (c) polymer phase separation/crystallization for photonics properties; (d) novel interpretations for phase separation or crystallization in polymers, copolymers, or blends; and (e) special phase behavior or surface-relief periodic patterns of polymers, blends or polymer–polymer complexes with potential applications as biomemetics, functional, biomedical, or photonic applications.

Although other potentially interesting topics are also welcome and not limited to the above lists, intended submissions should fall generally in line with phase behavior in polymers.

Prof. Dr. Eamor M. Woo
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

Phase behavior of blends or copolymers
Crystallization induced separation
Morphology
Self-assembly and surface relief patterns
Supramolecular architect

Published Papers (11 papers)

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Research

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14 pages, 2880 KiB

Open AccessArticle

Lateral Order and Self-Organized Morphology of Diblock Copolymer Micellar Films

by Jiun-You Liou and Ya-Sen Sun

Polymers 2018, 10(6), 597; https://0-doi-org.brum.beds.ac.uk/10.3390/polym10060597 - 29 May 2018

Viewed by 3704

Abstract

We report the lateral order and self-organized morphology of diblock copolymer polystyrene-block-poly(2-vinylpyridine), P(S-b-2VP), and micelles on silicon substrates (SiO_x/Si). These micellar films were prepared by spin coating from polymer solutions of varied concentration of polymer in toluene onto SiO_x/Si, and were investigated with grazing-incidence small-angle X-ray scattering (GISAXS) and an atomic force microscope (AFM). With progressively increased surface coverage with increasing concentration, loosely packed spherical micelles, ribbon-like nanostructures, and a second layer of spherical micelles were obtained sequentially. Quantitative analysis and simulations of the micellar packing demonstrates that the spatial ordering of the loosely packed spherical micelles altered from short-range order to hexagonal order when the micellar coverage increased from small to moderate densities of the covered surface. At large densities, anisotropic fusion between spherical micelles caused the ribbon-like nanostructures to have a short-range spatial order; the ordering quality of the second layer was governed by the rugged surface of the underlying layer because the valleys between the ribbon-like nanostructures allowed for further deposition of spherical micelles. Full article

(This article belongs to the Special Issue Phase Behavior in Polymers)

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11 pages, 4370 KiB

Open AccessArticle

Novel Magnetic-to-Thermal Conversion and Thermal Energy Management Composite Phase Change Material

by Xiaoqiao Fan, Jinqiu Xiao, Wentao Wang, Yuang Zhang, Shufen Zhang and Bingtao Tang

Polymers 2018, 10(6), 585; https://0-doi-org.brum.beds.ac.uk/10.3390/polym10060585 - 27 May 2018

Cited by 32 | Viewed by 4296

Abstract

Superparamagnetic materials have elicited increasing interest due to their high-efficiency magnetothermal conversion. However, it is difficult to effectively manage the magnetothermal energy due to the continuous magnetothermal effect at present. In this study, we designed and synthesized a novel Fe₃O₄/PEG/SiO₂ composite phase change material (PCM) that can simultaneously realize magnetic-to-thermal conversion and thermal energy management because of outstanding thermal energy storage ability of PCM. The composite was fabricated by in situ doping of superparamagnetic Fe₃O₄ nanoclusters through a simple sol–gel method. The synthesized Fe₃O₄/PEG/SiO₂ PCM exhibited good thermal stability, high phase change enthalpy, and excellent shape-stabilized property. This study provides an additional promising route for application of the magnetothermal effect. Full article

(This article belongs to the Special Issue Phase Behavior in Polymers)

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8 pages, 1284 KiB

Open AccessArticle

Determination of Pressure Dependence of Polymer Phase Transitions by pVT Analysis

by Jürgen Pionteck

Polymers 2018, 10(6), 578; https://0-doi-org.brum.beds.ac.uk/10.3390/polym10060578 - 24 May 2018

Cited by 19 | Viewed by 6487

Abstract

Glass transitions, melting, crystallization, and the isotropization of polymers are connected with changes in the density, respectively the specific volume (V_sp), which can be analyzed by dilatometric methods. Here, the pressure dependence of such transitions is determined by pressure volume temperature (pVT) analysis for different thermoplastic polymers in the pressure range of 10 to 200 MPa, and the temperature range from room temperature to 350 °C. The values for ambient pressure are extrapolated. It is shown that polymer transitions always increase with pressure, and that the melting temperature and glass transition temperature are nearly linearly dependent on pressure. This information, as well as the observed density changes with pressure and temperature, is very important for the processing of thermoplastics, including their simulation, as well as for the thermodynamic interpretations of the transition’s nature. Full article

(This article belongs to the Special Issue Phase Behavior in Polymers)

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21 pages, 12549 KiB

Open AccessArticle

Lamellae Assembly in Dendritic Spherulites of Poly(l-lactic Acid) Crystallized with Poly(p-Vinyl Phenol)

by Nurkhamidah Siti, Eamor M. Woo, Yu-Ting Yeh, Faliang Luo and Vimal Katiyar

Polymers 2018, 10(5), 545; https://0-doi-org.brum.beds.ac.uk/10.3390/polym10050545 - 18 May 2018

Cited by 12 | Viewed by 6525

Abstract

Lamellar assembly with fractal-patterned growth into dendritic and ringed spherulites of crystallized poly(l-lactic acid) (PLLA), of two molecular weight (MW) grades and crystallized at (temperature of crystallization) T_c = 120 and 130 °C, respectively, are evaluated using optical and atomic-force microscopies. The results of surface-relief patterns in correlation with interior microscopy analyses in this work strongly indicate that the observed birefringence changes in PLLA polymer dendritic or ringed spherulites (from blue to orange, or to optical extinction) need not be definitely associated with the continuous helix twisting of lamellae; they can be caused by sudden and discontinuous lamellae branching at intersected angles with respect to the original main lamellae, as proven in the case of dendritic and zig-zag rough-ringed spherulites. Intersection angles between the main stalks and branches tend to be governed by polymer crystal lattices; for PLLA, the orthorhombic lattice (α-form) usually gives a 60° angle of branching and hexagonal growth. The branching lamellae then further bend to convex or concave shapes and finally make a 60–90° angle with respect to the main stalks. Such mechanisms are proven to exist in the straight dendritic/striped high-molecular weight (HMW)-PLLA spherulites (T_c = 120 °C); similar mechanisms also work in circularly ringed (T_c = 130 °C) HMW-PLLA spherulites. Full article

(This article belongs to the Special Issue Phase Behavior in Polymers)

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14 pages, 45513 KiB

Open AccessArticle

Crystalline Modification and Its Effects on Dielectric Breakdown Strength and Space Charge Behavior in Isotactic Polypropylene

by Ling Zhang, Yunxiao Zhang, Yuanxiang Zhou, Chenyuan Teng, Zhaowei Peng and Stephen Spinella

Polymers 2018, 10(4), 406; https://0-doi-org.brum.beds.ac.uk/10.3390/polym10040406 - 05 Apr 2018

Cited by 18 | Viewed by 4342

Abstract

Adding nucleating agents (NAs) is one of the most efficient ways to obtain improved mechanical, optical, and thermal properties of isotactic polypropylene (iPP). While it is well appreciated that electrical property is critically affected by crystalline modification, the role between them remains unclear. Here, we address this issue by incorporating commercial α-NA and β-NA into iPP, both of which exhibit strong nucleation ability, e.g., reducing the size of crystalline agglomerates from 45.3 μm (Pure-iPP) to 2.5 μm (α-iPP) and 7.6 μm (β-iPP), respectively. Mechanical testing results show that while β-modification decreases the tensile strength a little, it does enhance the elongation at break (200%) and toughness (25.3% higher), relative to its unfilled counterparts. Moreover, a well-dispersed β-iPP system obtains a comprehensive improvement of electrical properties, including dielectric breakdown strength, space charge suppression, and internal field distortion under a high external field (−100 kV/mm) due to newly-generated deep charge trapping sites. This crystalline modification strategy is attractive for future development of many engineering insulating polymers. Full article

(This article belongs to the Special Issue Phase Behavior in Polymers)

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13 pages, 2670 KiB

Open AccessFeature PaperArticle

Minimizing the Strong Screening Effect of Polyhedral Oligomeric Silsesquioxane Nanoparticles in Hydrogen-Bonded Random Copolymers

by Wei-Cheng Chen, Ruey-Chorng Lin, Shih-Min Tseng and Shiao-Wei Kuo

Polymers 2018, 10(3), 303; https://0-doi-org.brum.beds.ac.uk/10.3390/polym10030303 - 11 Mar 2018

Cited by 16 | Viewed by 3742

Abstract

A series of poly(vinylphenol-co-methacryisobutyl polyhedral oligomeric silsesquioxane) (PVPh-co-PMAPOSS) random copolymers have been synthesized through free radical copolymerizations of acetoxystyrene with methacryisobutyl POSS monomer and subsequent hydrazine monohydrate-mediated hydrolysis of the acetoxyl units. These random copolymers were characterized using nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and differential scanning calorimetry (DSC), which revealed that the POSS content in the random copolymers could be varied by changing the POSS monomer feed ratio by ¹H NMR analyses. This molecular design approach allowed us to investigate the thermal properties and hydrogen bonding interactions of these PVPh-co-PMAPOSS random copolymers in comparison with those of PVPh/PMAPOSS blend systems. Hydrogen bonding interactions were absent in the PVPh/PMAPOSS blend system, because of a strong screening effect; in contrast, the PVPh-co-PMAPOSS random copolymers experienced enhanced intramolecular hydrogen bonding that minimized the strong screening effect of the POSS nanoparticles. Full article

(This article belongs to the Special Issue Phase Behavior in Polymers)

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12 pages, 7304 KiB

Open AccessArticle

Nucleation Enhancement in Stereodefective Poly(l-lactide) by Free Volume Expansion Resulting from Low-Temperature Pressure CO₂ Preconditioning

by Qiaofeng Lan, Jian Yu, Jun Zhang and Jiasong He

Polymers 2018, 10(2), 120; https://0-doi-org.brum.beds.ac.uk/10.3390/polym10020120 - 26 Jan 2018

Cited by 2 | Viewed by 3858

Abstract

Nucleation enhancement in a highly stereodefective poly(l-lactide) (PLLA) with an optical purity of 88% by low-temperature pressure (0 and 35 °C under 2 MPa) CO₂ preconditioning was investigated using differential scanning calorimetry (DSC), infrared (IR) spectroscopy, polarized optical microscopy (POM) as well as positron annihilation lifetime spectroscopy (PALS). Despite the preconditioning of the melt-quenched films for 2 h, IR results indicated that no trace of mesophase was generated and the samples remained in the glassy state. However, judging from the results of DSC, IR, and POM, when compared to the untreated sample, both the treated ones showed a significantly enhanced crystal nucleation effect, resulting in the corresponding greatly enhanced crystallization kinetics. Moreover, owing to the existence of the retrograde vitrification, the conditions of the previous low-pressure CO₂ conditioning affected the nucleation enhancement effect. When compared to the case of 35 °C, the much lower temperature of 0 °C was more effective for nucleation enhancement. The PALS results indicated that the enlarged free volume, which resulted from the CO₂ conditioning, largely accounted for the formation of locally ordered structures, providing many more potential nucleation sites for forming critical nuclei and thus the resulting enhanced crystallization kinetics in glassy PLLA. The present results have implications in understanding the nucleation enhancement effect, in particular in stereodefective PLLA systems, which possess extremely low crystallization ability and are thus probably too problematic to be evaluated by conventional methods. Full article

(This article belongs to the Special Issue Phase Behavior in Polymers)

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4692 KiB

Open AccessArticle

Macro-Micro Simulation for Polymer Crystallization in Couette Flow

by Chunlei Ruan, Kunfeng Liang and Enli Liu

Polymers 2017, 9(12), 699; https://0-doi-org.brum.beds.ac.uk/10.3390/polym9120699 - 11 Dec 2017

Cited by 4 | Viewed by 4338

Abstract

Polymer crystallization in manufacturing is a process where quiescent crystallization and flow-induced crystallization coexists, and heat/mass transfer on a macroscopic level interacts with crystal morphology evolution on a microscopic level. Previous numerical studies on polymer crystallization are mostly concentrated at a single scale; they only calculate macroscale parameters, e.g., temperature and relative crystallinity, or they only predict microstructure details, e.g., crystal morphology and mean size of crystals. The multi-scale numerical works that overcome these disadvantages are unfortunately based on quiescent crystallization, in which flow effects are neglected. The objective of this work is to build up a macro-micro model and a macro-micro algorithm to consider both the thermal and flow effects on the crystallization. Our macro-micro model couples two parts: mass and heat transfer of polymeric flow at the macroscopic level, and nucleation and growth of spherulites and shish-kebabs at the microscopic level. Our macro-micro algorithm is a hybrid finite volume/Monte Carlo method, in which the finite volume method is used at the macroscopic level to calculate the flow and temperature fields, while the Monte Carlo method is used at the microscopic level to capture the development of spherulites and shish-kebabs. The macro-micro model and the macro-micro algorithm are applied to simulate polymer crystallization in Couette flow. The effects of shear rate, shear time, and wall temperature on the crystal morphology and crystallization kinetics are also discussed. Full article

(This article belongs to the Special Issue Phase Behavior in Polymers)

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3539 KiB

Open AccessArticle

Prediction of Flow Effect on Crystal Growth of Semi-Crystalline Polymers Using a Multi-Scale Phase-Field Approach

by Xiaodong Wang, Jie Ouyang and Ying Liu

Polymers 2017, 9(12), 634; https://0-doi-org.brum.beds.ac.uk/10.3390/polym9120634 - 23 Nov 2017

Cited by 4 | Viewed by 4604

Abstract

A multi-scale phase-field approach, which couples the mesoscopic crystallization with the microscopic orientation of chain segments and macroscopic viscoelastic melt flow, is proposed to study how the crystal growth of semi-crystalline polymers is affected by flows. To make the simulation feasible, we divide the problem into three parts. In the first part, a finitely extensible nonlinear elastic (FENE) dumbbell model is used to simulate the flow induced molecular structure. In the second part, formulas for estimating the density, orientation and aspect ratio of nuclei upon the oriented molecular structure are derived. Finally, in the third part, a massive mathematical model that couples the phase-field, temperature field, flow field and orientation field is established to model the crystal growth with melt flow. Two-dimensional simulations are carried out for predicting the flow effect on the crystal growth of isotactic polystyrene under a plane Poiseuille flow. In solving the model, a semi-analytical method is adopted to avoid the numerical difficult of a “high Weissenberg number problem” in the first part, and an efficient fractional step method is used to reduce the computing complexity in the third part. The simulation results demonstrate that flow strongly affects the morphology of single crystal but does not bring a significant influence on the holistic morphology of bulk crystallization. Full article

(This article belongs to the Special Issue Phase Behavior in Polymers)

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6035 KiB

Open AccessArticle

How Chain Intermixing Dictates the Polymorphism of PVDF in Poly(vinylidene fluoride)/Polymethylmethacrylate Binary System during Recrystallization: A Comparative Study on Core–Shell Particles and Latex Blend

by Yue Li, Guoqiang Zhang, Shaofeng Song, Haijun Xu, Mingwang Pan and Gan-Ji Zhong

Polymers 2017, 9(9), 448; https://0-doi-org.brum.beds.ac.uk/10.3390/polym9090448 - 14 Sep 2017

Cited by 13 | Viewed by 7477

Abstract

In the past few decades, Poly(vinylidene fluoride)/Polymethylmethacrylate (PVDF/PMMA) binary blend has attracted substantial attention in the scientific community due to possible intriguing mechanical, optical and ferroelectric properties that are closely related to its multiple crystal structures/phases. However, the effect of PMMA phase on the polymorphism of PVDF, especially the relationship between miscibility and polymorphism, remains an open question and is not yet fully understood. In this work, three series of particle blends with varied levels of miscibility between PVDF and PMMA were prepared via seeded emulsion polymerization: PVDF–PMMA core–shell particle (PVDF@PMMA) with high miscibility; PVDF/PMMA latex blend with modest miscibility; and PVDF@c–PMMA (crosslinked PMMA) core–shell particle with negligible miscibility. The difference in miscibility, and the corresponding morphology and polymorphism were systematically studied to correlate the PMMA/PVDF miscibility with PVDF polymorphism. It is of interest to observe that the formation of polar β/γ phase during melt crystallization could be governed in two ways: dipole–dipole interaction and fast crystallization. For PVDF@PMMA and PVDF/PMMA systems, in which fast crystallization was unlikely triggered, higher content of β/γ phase, and intense suppression of crystallization temperature and capacity were observed in PVDF@PMMA, because high miscibility favored a higher intensity of overall dipole–dipole interaction and a longer interaction time. For PVDF@c–PMMA system, after a complete coverage of PVDF seeds by PMMA shells, nearly pure β/γ phase was obtained owing to the fast homogeneous nucleation. This is the first report that high miscibility between PVDF and PMMA could favor the formation of β/γ phase. Full article

(This article belongs to the Special Issue Phase Behavior in Polymers)

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Review

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34 pages, 20015 KiB

Open AccessReview

Polymorphic Behavior and Phase Transition of Poly(1-Butene) and Its Copolymers

by Rui Xin, Jie Zhang, Xiaoli Sun, Huihui Li, Zhongjie Ren and Shouke Yan

Polymers 2018, 10(5), 556; https://0-doi-org.brum.beds.ac.uk/10.3390/polym10050556 - 21 May 2018

Cited by 65 | Viewed by 7070

Abstract

The properties of semicrystalline polymeric materials depend remarkably on their structures, especially for those exhibiting a polymorphic behavior. This offers an efficient way to tailor their properties through crystal engineering. For control of the crystal structure, and therefore the physical and mechanical properties, a full understanding of the polymorph selection of polymers under varied conditions is essential. This has stimulated a mass of research work on the polymorphic crystallization and related phase transformation. Considering that the isotactic poly(1-butene) (iPBu) exhibits pronounced polymorphs and complicated transition between different phases, the study on its crystallization and phase transformation has attracted considerable attention during the past decades. This review provides the context of the recent progresses made on the crystallization and phase transition behavior of iPBu. We first review the crystal structures of known crystal forms and then their formation conditions and influencing factors. In addition, the inevitable form II to form I spontaneous transition mechanism and the transformation kinetics is reviewed based on the existing research works, aiming for it to be useful for its processing in different phases and the further technical development of new methods for accelerating or even bypass its form II to form I transformation. Full article

(This article belongs to the Special Issue Phase Behavior in Polymers)

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