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A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Macromolecular Crystals".

Deadline for manuscript submissions: closed (31 October 2021) | Viewed by 32746

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Dr. Jesús Sanmartín-Matalobos

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Inorganic Chemistry Department, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain
Interests: supramolecular chemistry; coordination chemistry; single crystal X-ray crystallography; H-bonding; chirality; fluorescence
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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,

The Section Macromolecular Crystals of Crystals provides a forum to report advancements in the understanding of the synthesis, nucleation, growth, processing, structure, properties, and applications of all classes of non-natural macromolecules, such as inorganic and organic polymers, or inorganic and organic large non-polymeric molecules.

The aim of this Special Issue on “Featured Papers in Macromolecular Crystals” is to make known relevant works to our colleagues in the macromolecular crystals field. To achieve this, the Special Issue edited by Jesús Sanmartín-Matalobos and Eamor M. Woo is inviting prominent scientists in the field to submit research articles, review articles as well as short communications focused on the synthesis, crystallization, characterization, properties, and theoretical aspects of macromolecular crystalline materials. The coverage of topics of this Special Issue is as broad as that of the Section Macromolecular Crystals, ranging from the synthesis, nucleation, growth, processing, and characterization of macromolecular crystalline materials to the mechanical, chemical, electrical, magnetic, catalytic, optical, and self-assembly properties, as well as their diverse applications. Among many other subject areas, the Section Macromolecular Crystals includes plastics, synthetic fibres, synthetic rubber, graphene carbon nanotubes, supramolecular polymers, polymer composites, metal coordination polymers, hybrid polymeric materials, metal–organic frameworks (MOFs), polymer–MOF hybrid materials, macrocycles, macrocyclic metal complexes, liquid crystals, and eutectic molecular liquids.

Therefore, we look forward to your valued contributions to make this Special Issue a reference resource of featured knowledge for future researchers in the Macromolecular Crystals field.

Prof. Dr. Jesús Sanmartín-Matalobos
Prof. Dr. Eamor M. Woo
Guest Editors

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Keywords

plastics
synthetic fibers
synthetic rubber
hybrid polymeric materials
eutectic molecular liquids
graphene carbon nanotubes
polymer composites
metal coordination polymers
metal–organic frameworks
macrocycles and macrocyclic metal complexes

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Published Papers (13 papers)

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Research

20 pages, 5859 KiB

Open AccessArticle

Physical-Mechanical Properties of Chartwell^® Coupling Agent-Treated Calcium Carbonate and Silica-Reinforced Hybrid Natural Rubber Composites

by Gabriel Deltrejo Ribeiro, Carlos Toshiyuki Hiranobe, José Francisco Resende da Silva, Giovanni Barrera Torres, Leonardo Lataro Paim, Aldo Eloizo Job, Flávio Camargo Cabrera and Renivaldo José dos Santos

Crystals 2022, 12(11), 1552; https://doi.org/10.3390/cryst12111552 - 30 Oct 2022

Cited by 5 | Viewed by 2938

Abstract

In this work investigated the possibility of applying a superficial treatment to ultra-fine calcium carbonate aiming to improve its interaction with the polymer chains of natural rubber so it does not act just as a filler. Commercial processes commonly use 40 phr of Silica as reinforcement filler. Here, we have evaluated the partial replacement of Silica by two types of calcium carbonate into hybrid natural rubber composites, untreated ultra-fine calcium carbonate and with ultra-fine calcium carbonate treated with 2% Chartwell C-515.71HR^®. We added calcium carbonate fillers to the composite mixtures (as replacements for commercial silica treated with silane) and studied their influence on the vulcanization process. According to our findings, between 25% and 75% of the silica can be replaced with treated calcium carbonate, and up to 30 parts of CaCO₃ can be combined with 100 parts of NR without compromising the properties of the polymer matrix (NR), which generates economic advantages for this industry. Treated calcium carbonate was able to link the inorganic and organic parts of the composite due to its bifunctionality; hence, it can be used as a filler to partially replace silica in hybrid NR composites. Full article

(This article belongs to the Special Issue Feature Papers in Macromolecular Crystals)

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12 pages, 3080 KiB

Open AccessArticle

Quantum Chemical Approach to the Adsorption of Chlorpyrifos and Fenitrothion on the Carbon-Doped Boron Nitride Nanotube Decorated with Tetrapeptide

by Chien-Lin Lee and Chia Ming Chang

Crystals 2022, 12(9), 1285; https://doi.org/10.3390/cryst12091285 - 11 Sep 2022

Cited by 2 | Viewed by 2094

Abstract

In the present study, four materials based on boron nitride nanotubes—namely pristine BNNT, C-doped BNNT, tetrapeptide/BNNT, and tetrapeptide/C-doped BNNT—were examined to evaluate adsorption of the organophosphorus pesticides chlorpyrifos and fenitrothion. Through a quantum chemical approach to the molecular and electronic structures, the impacts of C doping and tetrapeptide modification on boron nitride nanotubes are clarified. The results reveal that the tetrapeptide decoration does have the potential for differential sensing of chlorpyrifos and fenitrothion, but the improvement in the adsorption characteristics is slightly inferior to that of the C doping method. Nanosensors, such as C-doped BNNT and tetrapeptide/C-doped BNNT, are used to monitor chlorpyrifos and fenitrothion in solution phase, respectively. This quantum chemistry investigation has paved the way for the design of differential sensing devices for organophosphorus pesticides. Full article

(This article belongs to the Special Issue Feature Papers in Macromolecular Crystals)

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16 pages, 6446 KiB

Open AccessArticle

Thermal and Mechanical Characterization of Coir Fibre–Reinforced Polypropylene Biocomposites

by Mariana Ichim, Lucia Stelea, Ioan Filip, Gabriela Lisa and Emil Ioan Muresan

Crystals 2022, 12(9), 1249; https://doi.org/10.3390/cryst12091249 - 2 Sep 2022

Cited by 15 | Viewed by 3623

Abstract

In recent years, the growth of environmental awareness has increased the interest in the development of biocomposites which are sustainable materials with an excellent price–performance ratio and low weight. The current study aimed to obtain and characterize the biocomposites prepared by thermoforming using coir fibres as reinforcing material and polypropylene as matrix. The biocomposites were produced with different coir fibres/polypropylene ratios and were characterized by physical–mechanical indices, thermal analysis, crystallinity, attenuated total reflection-Fourier transform infrared spectroscopy analysis (ATR-FTIR), scanning electron microscopy (SEM), and chromatic measurements. Both tensile and bending strength of biocomposites decreased when the coir fibre content increased. The melting temperature of biocomposite materials has decreased with the increase of the coir fibre loading. Regarding the thermal stability, the weight loss and degradation temperature increased with decreasing coir fibre content. The ATR-FTIR and SEM analyses underlined the modifications that took place in the structure of the biocomposites by modifying the coir fibres/matrix ratio. Full article

(This article belongs to the Special Issue Feature Papers in Macromolecular Crystals)

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17 pages, 3313 KiB

Open AccessArticle

Theoretical Analysis of the Adsorption of Pentachlorophenol and 6-OH-BDE-47 (6-Hydroxy-2,2’,4,4’-Tetrabromodiphenyl Ether) by Boron Nitride Nanotubes Decorated with Double-Decker Lanthanide(III) Phthalocyanine Complexes

by Chien-Lin Lee, Shu-Chun Chi and Chia Ming Chang

Crystals 2022, 12(9), 1205; https://doi.org/10.3390/cryst12091205 - 27 Aug 2022

Viewed by 1908

Abstract

Environmental issues have become an urgent concern, and low-cost, high-efficiency environmental remediation and energy utilization are currently high priorities. In this work, zigzag (9,0) and (18,0) boron nitride nanotubes modified by double-decker lanthanide(III) phthalocyanine complexes (BN90-LnPc₂, BN180-LnPc₂) were investigated by semi-empirical quantum chemistry calculations. The shorter the bond length between the nitrogen atom in the complex and the hydroxyl group of the contaminant, the greater the change in the C-O-H bond angle, implying stronger adsorption. In view of the neutral and deprotonated forms of pentachlorophenol and 6-OH-BDE-47 (6-Hydroxy-2,2’,4,4’-tetrabromodiphenyl ether), the effects of the hydrogen bond on the contaminants were significantly different. The analytical results of the HSAB reactivity descriptors and frontier molecular orbitals showed that BN180-YbPc₂ performed best of all the composite systems, and the interaction with pentachlorophenol was stronger than with 6-OH-BDE-47. Furthermore, BN180-YbPc₂ is beneficial as a solar-energy material, according to its electronic excitation spectrum. Ultimately, the calculated results were as expected due to the materials’ multifunctional characteristics, and the exploration of material development for specific properties will be the direction for future work. Full article

(This article belongs to the Special Issue Feature Papers in Macromolecular Crystals)

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13 pages, 823 KiB

Open AccessArticle

Effect of Additional Dry Heat Curing on Microflexural Strength in Three Types of Resin Composite: An In Vitro Study

by Marlon Zamalloa-Quintana, Carlos López-Gurreonero, Flor Magaly Santander-Rengifo, Marysela Ladera-Castañeda, Antonieta Castro-Pérez Vargas, Alberto Cornejo-Pinto, Luis Cervantes-Ganoza and César Cayo-Rojas

Crystals 2022, 12(8), 1045; https://doi.org/10.3390/cryst12081045 - 27 Jul 2022

Cited by 4 | Viewed by 2279

Abstract

Aim: Additional dry heat curing is a method that favorably influences the mechanical properties of an indirect resin composite restoration. Microflexural strength is a property currently applied for the evaluation of indirect resin composite restorations. The aim of the present study was to assess the effect of additional dry heat curing on microflexural strength in three types of direct-use resin composites. Materials and Methods: This in vitro study consisted of 70 resin composites samples made with a 6 × 2 × 1 mm metal matrix and divided into seven experimental groups, which included Gr1a: Tetric N-Ceram without additional dry heat curing (n = 10); Gr1b: Tetric N-Ceram with additional dry heat curing (n = 10); Gr 2a: Filtek Z350 XT without additional dry heat curing (n = 10); Gr2b: Filtek Z350 XT with additional dry heat curing (n = 10); Gr3a: Filtek Z250 without additional dry heat curing (n = 10); Gr3b: Filtek Z250 with additional dry heat curing (n = 10); and Gr4: SR Nexco Paste (control) without additional dry heat curing (n = 10). The samples were stored in distilled water at 37 °C for 24 h. A universal testing machine with a 2000 N load cell at a speed of 1 mm/min was used to assess flexural strength. The data were analyzed with a parametric ANOVA test with Tukey’s post hoc intergroup factor (for groups without heat treatment) and a nonparametric Kruskall Wallis test with Bonferroni’s post hoc (for groups with heat treatment). In addition, the comparison of independent groups in each resin composite type with and without heat treatment was performed with a Mann Whitney U test. A significance level of p < 0.05 was considered. Results: The Filtek Z250 resin composite with and without additional dry heat curing presented the highest microflexural strength values with 137.27 ± 24.43 MPa and 121.32 ± 9.74 MPa, respectively, while the SR Nexco Paste (control) resin composite presented the lowest microflexural strength values with 86.06 ± 14.34 MPa compared to all the resin composites with additional dry heat curing. The Filtek Z250 and Filtek Z350XT resin composites with and without additional dry heat curing presented significantly higher microflexural strength versus the SR Nexco (p < 0.05) and Tetric N-Ceram (p < 0.05) resin composites. In addition, the Filtek Z350XT and Tetric N-Ceram resin composites with additional dry heat curing showed significantly higher microflexural strength (p < 0.05) compared to those without additional dry heat curing. Conclusions: The Filtek Z250 and Z350XT resin composites had significantly higher microflexural strength values with and without additional dry heat curing. In addition, the Filtek Z350XT and Tetric N-Ceram resin composites subjected to additional dry heat curing showed significantly higher microflexural strength compared to when they did not receive the same procedure, a situation that did not occur with the Filtek Z250 resin composite. Full article

(This article belongs to the Special Issue Feature Papers in Macromolecular Crystals)

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12 pages, 3455 KiB

Open AccessArticle

Incorporation of Rhodamine into a Host Polymer via In-Situ Generated Isocyanato Group and Application for the Detection of Cu²⁺ Ion

by Sai Zhang, Zhe Yao, Wenqiang Qiao and Zhi Yuan Wang

Crystals 2022, 12(6), 841; https://doi.org/10.3390/cryst12060841 - 15 Jun 2022

Cited by 3 | Viewed by 2202

Abstract

A rhodamine-based fluorescent polymer P(MMA-co-RB) has been synthesized via an intermediate NCO-containing polymer generated by the Lossen rearrangement reaction. The fluorescent property of P(MMA-co-RB) with regard to metal ions, such as Cu²⁺, Fe³⁺, Cr³⁺, Al³⁺, Zn²⁺, Co²⁺, Sn²⁺ and Ag⁺, was studied by fluorescence emission spectroscopy. The results demonstrate that the fluorescence intensity of P(MMA-co-RB) decreased gradually with an increase of the concentration of Cu²⁺ ion. Furthermore, a test strip made of P(MMA-co-RB) can be used for fast and quantitative determination of Cu²⁺ ion. In the presence of Cu²⁺ ion, the sensory tester undergoes distinct changes in fluorescence intensity and visible color. Full article

(This article belongs to the Special Issue Feature Papers in Macromolecular Crystals)

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13 pages, 6253 KiB

Open AccessArticle

Morphology Modulation in Self-Assembly of Chiral 2-Hydroxy-2-Phenylacetic Acids in Polymeric Diluents

by Baiq Firyal Salsabila Safitri and Eamor M. Woo

Crystals 2022, 12(6), 807; https://doi.org/10.3390/cryst12060807 - 7 Jun 2022

Cited by 1 | Viewed by 1859

Abstract

This study focused on the chirality effects that control the lamellar bending sense in self-assembled crystals of chiral 2-hydroxy-2-phenylacetic acids. 2-Hydroxy-2-phenylacetic acid or mandelic acid (MA) was crystallized in the presence of poly(4-vinyl phenol) (PVPh), and its crystalline structures and morphologies were assessed using polarized optical microscopy (POM) and scanning electron microscopy (SEM). MA of two opposite chiral forms (S- and R-) was crystallized with PVPh as the morphology modulator; with adjustment of the PVPh content, the morphology of MA crystals transforms from ring-banded spherulites to highly dendritic spherulites. For MA/PVPh (50/50 wt./wt.) blend and neat MA at same T_c, the dendritic spherulites are packed with single crystals where the lamellae bend at a specific direction varying with T_c and chirality. Contrary to conventional thought, the bending senses of the MA lamellae in the dendritic spherulites are not solely governed by the MA molecular chirality (S or R), but also by T_c. Only at high T_c (>65 °C) is the lamellar bending direction in dendritic spherulites of (S)-MA or (R)-MA blended with PVPh dictated by the chirality, i.e., displaying counterclockwise and clockwise bending direction for (S)-MA/PVPh and (R)-MA/PVPh, respectively. Nevertheless, at low T_c (45 °C), the bending sense of dendritic spherulites displays an opposite direction from those at the higher T_c, which is to say that the chirality alone does not control the lamellar bending direction. Full article

(This article belongs to the Special Issue Feature Papers in Macromolecular Crystals)

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11 pages, 1851 KiB

Open AccessArticle

Controlled Synthesis and Photoresponsive Properties of Spiropyran End-Functionalized Poly(vinyl ether)s

by Jin Motoyanagi, Ayane Fujishima and Masahiko Minoda

Crystals 2022, 12(5), 742; https://doi.org/10.3390/cryst12050742 - 22 May 2022

Viewed by 2444

Abstract

Due to the need to develop smart materials for a variety of applications such as catalysts and drug delivery, the development of photoresponsive polymers is receiving increasing attention. In particular, the photoisomerization of spiropyran (SP), unlike many other photoresponsive compounds, has attracted attention because it dramatically changes not only the molecular structure but also the polarity of the molecule. However, in most cases where SP is used as a photoresponsive functional group, SP is introduced in the side chain of the polymer, and few cases have been reported in which SP is introduced at the end of the polymer chain. Therefore, we designed a new amphipathic poly(vinyl ether) with an SP moiety at the end of the polymer chain. First, an initiator having an SP moiety was synthesized and used for living cationic polymerization to synthesize a poly(vinyl ether) bearing an SP moiety at the end of the polymer chain. Furthermore, we investigated the photoresponsive properties of the obtained polymers, we found that self-assembly of the amphiphilic polymers could be controlled by photoirradiation. Full article

(This article belongs to the Special Issue Feature Papers in Macromolecular Crystals)

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15 pages, 6976 KiB

Open AccessFeature PaperArticle

Fabrication, Design and Characterization of 1D Nano-Fibrous SiO₂ Surface by a Facile and Scalable Method

by Lahcen Khouchaf and Abdelhamid Oufakir

Crystals 2022, 12(4), 531; https://doi.org/10.3390/cryst12040531 - 10 Apr 2022

Cited by 5 | Viewed by 2076

Abstract

In this paper, new 1D nano-fibrous SiO₂ with functionalized surfaces is prepared. First, the effect of dispersion on the morphology and the surface properties of the silica SiO₂ compounds are investigated. Second, energy dispersive spectrometer (EDS) and variable pressure scanning electron microscope (VP-SEM) show typically pure and fibrous texture on the surface of SiO₂. Third, the presence of the bridging oxygen stretching vibration Si-O-Si, as well as the increase in the intensity ratio between Si-OH band and Si-O-Si are revealed by (FTIR) spectroscopy. Furthermore, X-ray diffraction (XRD) validates the conservation of the SiO lattice after chemical treatment through the KOH for both dispersed and non-dispersed samples. In addition, the shift of the XRD main peak (101) is in good agreement with the FTIR results showing the shift of Si-O-Si peak and the increase in the intensity ratio of Si-OH/Si-O-Si. The dispersed SiO₂ sample exhibits a promising functionalized surface with satisfactory results in terms of silica nanofibers crystallinity and chemical composition. As a result, gigh resolution transmission electron microscopy (HR-TEM) data corroborate the claim of the presence of SiO₂ nanofibers on the surface from 20 nm to 250 nm. New nano-fibrous SiO₂ surfaces will be used to improve interfacial bonding strength between SiO₂ compounds and polymer (or organic materials). Full article

(This article belongs to the Special Issue Feature Papers in Macromolecular Crystals)

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10 pages, 1439 KiB

Open AccessCommunication

Influence of Precursor Density and Conversion Time on the Orientation of Vapor-Deposited ZIF-8

by Marianne Kräuter, Alexander John Cruz, Timothée Stassin, Sabina Rodríguez-Hermida, Rob Ameloot, Roland Resel and Anna Maria Coclite

Crystals 2022, 12(2), 217; https://doi.org/10.3390/cryst12020217 - 1 Feb 2022

Cited by 10 | Viewed by 3037

Abstract

ZIF-8 was synthesized by subjecting ZnO thin films deposited via plasma-enhanced atomic layer deposition to a 2-methylimidazole vapor. The impact of the conversion time as well as the density and thickness of the ZnO precursor on the resulting ZIF-8 layers were investigated. Grazing Incidence X-ray diffraction reveals a preferred (100) or (111) orientation of the ZIF-8 crystals, depending on thickness and density of the precursor, and with a more prominent orientation at longer conversion times. The onset of crystallization occurs after 20 min of conversion for the less dense precursor, compared to 40 min for the denser one. The ZIF-8 thickness and roughness increase with conversion time. The final thickness of the ZIF-8 layer depends on the thickness and density of the precursor layer, and can be up to 15-fold higher than the precursor thickness. Full article

(This article belongs to the Special Issue Feature Papers in Macromolecular Crystals)

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16 pages, 8680 KiB

Open AccessArticle

In-Situ Growth of Nucleus Geometry to Dual Types of Periodically Ringed Assemblies in Poly(nonamethylene terephthalate)

by Eamor M. Woo, Chien-Hua Tu, Selvaraj Nagarajan and Graecia Lugito

Crystals 2021, 11(11), 1338; https://doi.org/10.3390/cryst11111338 - 2 Nov 2021

Cited by 3 | Viewed by 2684

Abstract

Monitoring of nucleus geometry and growth into dual types of periodically ring-banded morphology in poly(nonamethylene terephthalate) (PNT), respectively, Type-1 and Type-2, are done with detailed analyses using polarized-light optical microscopy (POM) in-situ CCD recording; the periodic assembly morphologies are characterized using atomic-force microscopy (AFM) and scanning electron microscopy (SEM). Different annealing treatments (T_max = 110, 120, 130 °C) are accomplished at a crystallization temperature of 85 °C; effects on the nucleus geometry, number (25–10%) and volume fractions (33–15%) of Type-2 among two types of banded PNT spherulites are expounded. Growth of a specific type of periodically banded PNT spherulite is initiated from either highly elongated sheaf-like or well-rounded nuclei, with the final grown lamellae being self-packed as multi-shell structures. Nucleation geometry and crystallization parameters collectively lead to development of multiple types of banded PNT spherulites of different relative fractions. Full article

(This article belongs to the Special Issue Feature Papers in Macromolecular Crystals)

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12 pages, 2580 KiB

Open AccessArticle

Crystallization Behaviors of Composites Comprising Biodegradable Polyester and Functional Nucleation Agent

by Li-Ting Lee, Hsiang-Yun Tseng and Tzi-Yi Wu

Crystals 2021, 11(10), 1260; https://doi.org/10.3390/cryst11101260 - 18 Oct 2021

Cited by 5 | Viewed by 2030

Abstract

In this study, a thorough study of the crystallization behaviors of the biodegradable polymer composites of poly(ethylene succinate) (PESu) and hexagonal boron nitride (h-BN) was carried out. We found that h-BN had a significant nucleation effect on crystallization behaviors. DSC isothermal crystallization results demonstrated that the crystallization time of the PESu/h-BN composites became shorter after adding h-BN. The rate constant k values calculated from the Avrami equation were larger for the composites, demonstrating that PESu’s crystallization rate was increased by adding h-BN. TEM and SEM images showed the well-dispersed h-BN in the PESu matrix. Optical microscopy revealed that the PESu/h-BN composites formed more and smaller spherulites than neat PESu did, which confirmed that h-BN caused the nucleation effect. H-BN also accelerated non-isothermal crystallization kinetics. We discussed the behaviors of the Mo model, which demonstrated that h-BN promoted the kinetics of non-isothermal crystallization. The XRD diffraction patterns showed that h-BN in the composites would not obviously change the crystalline structure of PESu. Full article

(This article belongs to the Special Issue Feature Papers in Macromolecular Crystals)

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10 pages, 3220 KiB

Open AccessCommunication

Enhancement of Crystallization Behaviors in Quaternary Composites Containing Biodegradable Polymer by Supramolecular Inclusion Complex

by Li-Ting Lee, Sheng-Ping He and Chih-Feng Huang

Crystals 2020, 10(12), 1137; https://doi.org/10.3390/cryst10121137 - 12 Dec 2020

Cited by 3 | Viewed by 2137

Abstract

Novel multi-component composites composed of the biodegradable polymer poly(ethylene adipate) (PEA), the water-soluble polymer poly(ethylene oxide) (PEO), poly(vinyl acetate) (PVAc), and a supramolecular-like inclusion complex (IC) made by α-cyclodextrin (α-CD) and poly(ε-caprolactone) (PCL) (coded as PCL–CD–IC) are discussed in this work. The PCL–CD–IC was used to increase the crystallization rate of the miscible PEA/PEO/PVAc ternary blend that crystalized slower than neat PEA. Higher resolution SEM and TEM images displayed that PCL–CD–IC did not assemble notably in the quaternary composites. For the results of isothermal crystallization, the analysis of the Avrami equation demonstrated that the rate constant k increased with the addition of PCL–CD–IC in the composites, suggesting that PCL–CD–IC provided more nucleation sites to promote the crystallization rate. The nucleation density increased with the addition of PCL–CD–IC, and the amount of spherulite also increased. Wide angle X-ray results showed that the composites displayed similar diffraction patterns to neat PEA, meaning PEO, PVAc, and PCL–CD–IC would not change the crystal structures of PEA in the composites. The PCL–CD–IC, the supramolecular nucleation agent, demonstrated its superior ability to enhance the multi-component composites of biodegradable polymer in this study. Full article

(This article belongs to the Special Issue Feature Papers in Macromolecular Crystals)

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