Special Issue "Polymer Structure and Property"

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

Deadline for manuscript submissions: closed (31 December 2019).

Special Issue Editors

Dr. Michelina Soccio
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Guest Editor
Department of Civil, Chemical, Environmental and Materials Engineering, University of Bologna, Via Terracini 28, 40131 Bologna, Italy
Interests: polymers; polyesters; biopolymers; copolymers; soft tissue engineering; food packaging; polymer crystallization; polymer dynamics
Special Issues and Collections in MDPI journals
Prof. Dr. Nadia Lotti
Website
Guest Editor
Department of Civil, Chemical, Environmental and Materials Engineering, University of Bologna, Via Terracini 28, 40131 Bologna, Italy
Interests: polyesters; synthesis; chemical modification; thermal properties; mechanical properties; barrier properties; biodegradability; packaging; tissue engineering; controlled nanodrug delivery systems
Special Issues and Collections in MDPI journals

Special Issue Information

Dear colleagues,

The increasing use of polymers in different fields has stimulated the search for versatile polymeric structures covering a wide range of properties. In this context, a fundamental knowledge of the structure–property relations is mandatory. The establishment of these correlations implies that we must consider the chemical structure and the architectural aspects. The former are related to the polymer fine structure, i.e. the type of monomeric unit forming the chain that affects the sample crystallinity and the physical properties. The latter concern the chain as a whole, i.e. considering the presence of branching, crosslinking, distribution of chain length, chain conformation and rigidity. The knowledge of such correlations will indicate the suitability of a polymer for a particular purpose. In particular, this depends on whether it is glass-like, rubber-like or fiber-forming, according to chain flexibility, chain symmetry, and intermolecular attractions.

The aim of this Special Issue is to collect research or review papers, in order to understand the state of the art as well as to obtain insight into the possible correlations between the structure and properties of polymers. All contributions related to this issue are welcome.

Prof. Michelina Soccio
Prof. Nadia Lotti
Guest Editors

Keywords

  • solid state properties
  • polymer modification
  • polymer crystallization
  • molecular dynamics
  • mechanical properties

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Published Papers (10 papers)

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Research

Open AccessArticle
Enthalpy Relaxation, Crystal Nucleation and Crystal Growth of Biobased Poly(butylene Isophthalate)
Polymers 2020, 12(1), 235; https://doi.org/10.3390/polym12010235 - 18 Jan 2020
Abstract
The crystallization behavior of fully biobased poly(butylene isophthalate) (PBI) has been investigated using calorimetric and microscopic techniques. PBI is an extremely slow crystallizing polymer that leads, after melt-crystallization, to the formation of lamellar crystals and rather large spherulites, due to the low nuclei [...] Read more.
The crystallization behavior of fully biobased poly(butylene isophthalate) (PBI) has been investigated using calorimetric and microscopic techniques. PBI is an extremely slow crystallizing polymer that leads, after melt-crystallization, to the formation of lamellar crystals and rather large spherulites, due to the low nuclei density. Based upon quantitative analysis of the crystal-nucleation behavior at low temperatures near the glass transition, using Tammann’s two-stage nuclei development method, a nucleation pathway for an acceleration of the crystallization process and for tailoring the semicrystalline morphology is provided. Low-temperature annealing close to the glass transition temperature (Tg) leads to the formation of crystal nuclei, which grow to crystals at higher temperatures, and yield a much finer spherulitic superstructure, as obtained after direct melt-crystallization. Similarly to other slowly crystallizing polymers like poly(ethylene terephthalate) or poly(l-lactic acid), low-temperature crystal-nuclei formation at a timescale of hours/days is still too slow to allow non-spherulitic crystallization. The interplay between glass relaxation and crystal nucleation at temperatures slightly below Tg is discussed. Full article
(This article belongs to the Special Issue Polymer Structure and Property)
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Open AccessArticle
Comprehensive Analysis of Mechanical Properties of CB/SiO2/PVDF Composites
Polymers 2020, 12(1), 146; https://doi.org/10.3390/polym12010146 - 07 Jan 2020
Abstract
Damage is a key problem that limits the application of polymer membranes. In this paper, conductive carbon black (CB) and silicon dioxide (SiO2)-reinforced polyvinylidene fluoride (PVDF) composites were prepared using a solution mixing method. Through a uniaxial tensile test, the fracture [...] Read more.
Damage is a key problem that limits the application of polymer membranes. In this paper, conductive carbon black (CB) and silicon dioxide (SiO2)-reinforced polyvinylidene fluoride (PVDF) composites were prepared using a solution mixing method. Through a uniaxial tensile test, the fracture and damage characteristics of the material were analyzed. When the structure had inevitable notch damage, changing the notch angle was very helpful for the material to bear more load. In addition, when there were two kinds of fillers in the PVDF matrix at the same time, there was an interaction between particles. The microstructure of the composite was characterized by scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), and thermogravimetric (TG) analysis. The experimental results indicate that, when the ratio of CB:SiO2:PVDF was 1:4:95, the general mechanical properties of the composite were the best. Full article
(This article belongs to the Special Issue Polymer Structure and Property)
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Open AccessArticle
Synthesis and Properties of Cyclopentyl Cardo-Type Polyimides Based on Dicyclopentadiene
Polymers 2019, 11(12), 2029; https://doi.org/10.3390/polym11122029 - 06 Dec 2019
Abstract
A crucial polymer intermediate, 4-[1-(4-hydroxyphenyl)cyclopentyl]-phenol (bisphenol CP), was developed from dicyclopentadiene (DCPD), a key byproduct of the C5 fraction in petrochemicals. On the basis of bisphenol CP, a diamine, 4,4′-((cyclopentane-1,1-diylbis(4,1-phenylene))bis(oxy))-dianiline (cyclopentyl diamine; CPDA) was subsequently obtained through a nucleophilic substitution of bisphenol CP, [...] Read more.
A crucial polymer intermediate, 4-[1-(4-hydroxyphenyl)cyclopentyl]-phenol (bisphenol CP), was developed from dicyclopentadiene (DCPD), a key byproduct of the C5 fraction in petrochemicals. On the basis of bisphenol CP, a diamine, 4,4′-((cyclopentane-1,1-diylbis(4,1-phenylene))bis(oxy))-dianiline (cyclopentyl diamine; CPDA) was subsequently obtained through a nucleophilic substitution of bisphenol CP, followed by the hydrogenation process. By using the CPDA diamine, a series of polyimides with cyclopentyl (cardo) units on the backbone were prepared along with a reference polyimide (API-6F) based on 4,4′-(4,4′-(propane-2,2-diyl)bis(4,1-phenylene))bis(oxy)dianiline (BPAA), and 4,4′-(hexafluoroisopropylidene)-diphthalic anhydride (6FDA) for the exploration of structure-properties relationship. Thanks to the presence of cyclopentyl units, this type of cardo polyimides exhibited comparable tensile properties, especially a large elongation (25.4%). It is also worth noting that CPI-6F exhibited better solubility in organic solvents, such as NMP, DMAc, THF, and chloroform, than the other PIs. Gas separation properties were also evaluated for these cardo-type polyimides. Full article
(This article belongs to the Special Issue Polymer Structure and Property)
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Open AccessArticle
Crystalline Modification of Isotactic Polypropylene with a Rare Earth Nucleating Agent Based on Ultrasonic Vibration
Polymers 2019, 11(11), 1777; https://doi.org/10.3390/polym11111777 - 29 Oct 2019
Abstract
In this paper, the crystalline modification of isotactic polypropylene (PP) with a rare earth β nucleating agent (WBG) with different ultrasound conditions was investigated by scanning electron microscopy (SEM), wide-angle X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The relationship between the ultrasound [...] Read more.
In this paper, the crystalline modification of isotactic polypropylene (PP) with a rare earth β nucleating agent (WBG) with different ultrasound conditions was investigated by scanning electron microscopy (SEM), wide-angle X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The relationship between the ultrasound conditions and the crystalline structure, as well as the mechanism for the behavior, were revealed. SEM showed that the dispersion of the nucleating agent in the PP matrix was better at shorter ultrasound distances. In addition, the higher the water cooling temperature, the better the nucleating agent was dispersed in the PP matrix. The results of XRD and DSC showed that the crystallinity and the relative content of the β-crystal were increased with nearer ultrasound distance, as well as increased in higher water cooling temperatures. In particular, under the same conditions, the crystallinity and the relative content of the β-crystal after ultrasonic treatment were much higher than those without ultrasound. Full article
(This article belongs to the Special Issue Polymer Structure and Property)
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Open AccessArticle
Assessment of Compressive Mechanical Behavior of Bis-GMA Polymer Using Hyperelastic Models
Polymers 2019, 11(10), 1571; https://doi.org/10.3390/polym11101571 - 27 Sep 2019
Abstract
Despite wide industrial applications of Bis-GMA polymer, very few studies are available about the material classification, mechanical properties, and behavior of this material. In this study, the compressive behavior of Bis-GMA polymer was studied using different hyperelastic constitutive models through a hybrid experimental-computational [...] Read more.
Despite wide industrial applications of Bis-GMA polymer, very few studies are available about the material classification, mechanical properties, and behavior of this material. In this study, the compressive behavior of Bis-GMA polymer was studied using different hyperelastic constitutive models through a hybrid experimental-computational process. Standard uniaxial compression tests were conducted to extract the mechanical behavior and structural response of the Bis-GMA polymer. A nano-indentation experiment was used to verify the compressive behavior of Bis-GMA polymer in the form of hyperelastic behavior. The finite element model and real-time simulation of the test incorporating different hyperelastic models were developed in comparison with the experimental finding to obtain the proper type of hyperelastic behavior of Bis-GMA polymer. The results indicate that a second-order polynomial hyperelastic model is the best fit to predict the behavior of Bis-GMA polymer. Next, the validated model was used to determine the true stress–strain curve of the Bis-GMA polymer. Full article
(This article belongs to the Special Issue Polymer Structure and Property)
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Open AccessArticle
Synthesis, Thermal Properties and Curing Kinetics of Hyperbranched BPA/PEG Epoxy Resin
Polymers 2019, 11(10), 1545; https://doi.org/10.3390/polym11101545 - 23 Sep 2019
Cited by 3
Abstract
The hyperbranched epoxy resins (HBE) composed of bisphenol A (BPA) and polyethylene glycol (PEG) as reactants and pentaerythritol as branching point were successfully synthesized via A2 + B4 polycondensation reaction at various BPA/PEG ratios. The 13C NMR spectra revealed that [...] Read more.
The hyperbranched epoxy resins (HBE) composed of bisphenol A (BPA) and polyethylene glycol (PEG) as reactants and pentaerythritol as branching point were successfully synthesized via A2 + B4 polycondensation reaction at various BPA/PEG ratios. The 13C NMR spectra revealed that the synthesized HBE mainly had a dendritic structure as confirmed by the high degree of branching (DB). The addition of PEG in the resin enhanced degree of branching (DB) (from 0.82 to 0.90), epoxy equivalent weight (EEW) (from 697 g eq−1 to 468 g eq−1) as well as curing reaction. Adding 5–10 wt.% PEG in the resin decreased the onset and peak curing temperatures and glass transition temperature; however, adding 15 wt.% PEG in the resin have increased these thermal properties due to the lowest EEW. The curing kinetics were evaluated by fitting the experimental data of the curing behavior of all resins with the Šesták–Berggren equation. The activation energy increased with the increase of PEG in the resins due to HBE’s steric hindrance, whereas the activation energy of HBE15P decreased due to a large amount of equivalent active epoxy group per mass sample. The curing behavior and thermal properties of obtained hyperbranched BPA/PEG epoxy resin would be suitable for using in electronics application. Full article
(This article belongs to the Special Issue Polymer Structure and Property)
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Open AccessArticle
Structure and Physicochemical Properties of Malate Starches from Corn, Potato, and Wrinkled Pea Starches
Polymers 2019, 11(9), 1523; https://doi.org/10.3390/polym11091523 - 19 Sep 2019
Cited by 1
Abstract
In this study, corn, potato, and wrinkled pea starches were esterified with malic acid under high temperatures for different lengths of time. The degree of substitution (DS), granule morphology, crystal structure, gelatinization properties, and the digestibility of the malate starch were investigated. Fourier [...] Read more.
In this study, corn, potato, and wrinkled pea starches were esterified with malic acid under high temperatures for different lengths of time. The degree of substitution (DS), granule morphology, crystal structure, gelatinization properties, and the digestibility of the malate starch were investigated. Fourier transform infrared spectroscopy (FT–IR) suggested that the malate starch showed a new infrared absorption peak near 1747 cm−1, indicating the occurrence of an esterification reaction. With an increasing treatment time, the degree of substitution (DS) of the malate starch displayed an increasing trend. Scanning electron microscopy (SEM) demonstrated a significant change in the surface structure of the starch granules. X-ray diffractometry (XRD) reflected that the crystal structure of the malate starches was destroyed. The thermogravimetric (TG) curves showed that the maximum heat loss rate of the malate starch was ahead of that of native starch, which caused the decreased degree of crystallinity. These properties of malate starch could allow it to be used for the purpose of starch modification to produce resistant starch and to provide new applications for starch. Full article
(This article belongs to the Special Issue Polymer Structure and Property)
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Open AccessArticle
Synthesis of Intelligent pH Indicative Films from Chitosan/Poly(vinyl alcohol)/Anthocyanin Extracted from Red Cabbage
Polymers 2019, 11(7), 1088; https://doi.org/10.3390/polym11071088 - 26 Jun 2019
Cited by 1
Abstract
In this study, pH indicative films were successfully synthesized from hydrogels made by blending 1% poly(vinyl alcohol) (PVA) and 1% chitosan (CS) with anthocyanin (ATH) and sodium tripolyphosphate (STPP). Particularly, ATH extracted from red cabbage was used as the pH indicator, while STPP [...] Read more.
In this study, pH indicative films were successfully synthesized from hydrogels made by blending 1% poly(vinyl alcohol) (PVA) and 1% chitosan (CS) with anthocyanin (ATH) and sodium tripolyphosphate (STPP). Particularly, ATH extracted from red cabbage was used as the pH indicator, while STPP was utilized as the cross-linking agent to provide better mechanical properties of the cast films. FT-IR spectra confirmed the existence of the ATH in the cast films. Moreover, the tensile strength, the elongation-at-break, and the swelling indices of the cast films were measured. In general, these properties of pH indicative films were profoundly influenced by the compositions of PVA/CS and the STPP dosage applied in the hydrogels. For example, the tensile strength could change from 43.27 MPa on a film cast from pure PVA hydrogel to 29.89 MPa, if 35% of the PVA hydrogel was substituted with CS. The cast films were applied as a food wrap that could be used to monitor visually the quality of the enwrapped food via the color change of the film upon the variation in pH values of the enwrapped food. In practice, a sequential change in color was successfully observed on the pH indicative films partially enwrapping the pork belly, indicating the spoilage of the meat. Full article
(This article belongs to the Special Issue Polymer Structure and Property)
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Open AccessEditor’s ChoiceArticle
The Thermal and Mechanical Properties of Poly(ethylene-co-vinyl acetate) Random Copolymers (PEVA) and its Covalently Crosslinked Analogues (cPEVA)
Polymers 2019, 11(6), 1055; https://doi.org/10.3390/polym11061055 - 17 Jun 2019
Cited by 1
Abstract
The thermal and mechanical properties of poly(ethylene-co-vinyl acetate) random copolymers (PEVA) and its covalently crosslinked analogues (cPEVA) were controlled by the overall crystallinity of the polymer networks. The cPEVAs with different VA-content were synthesized by thermally-induced crosslinking of linear PEVA with [...] Read more.
The thermal and mechanical properties of poly(ethylene-co-vinyl acetate) random copolymers (PEVA) and its covalently crosslinked analogues (cPEVA) were controlled by the overall crystallinity of the polymer networks. The cPEVAs with different VA-content were synthesized by thermally-induced crosslinking of linear PEVA with dicumyl peroxide (DCP). This work was mainly concerned with the effect of vinyl acetate (VA) content on the crosslinking density, thermal and mechanical properties of PEVAs and cPEVAs, respectively. The chemical composition was analyzed by thermogravimetric analysis and 1H-NMR. The thermal and mechanical properties of PEVAs and cPEVAs have been studied through a series of conventional analytical methods, including gel content determination, different scanning calorimetry, thermogravimetric analysis, dynamic mechanical thermal analysis and traditional mechanical measurements. The experimental results show that the thermal and mechanical properties of PEVAs and cPEVAs increase with decreasing the VA-content. A broad melting transition with a ΔTm in the range from 78 °C to 95 °C was observed for all polymer networks. Full article
(This article belongs to the Special Issue Polymer Structure and Property)
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Open AccessArticle
Effects of Diisocyanate Structure and Disulfide Chain Extender on Hard Segmental Packing and Self-Healing Property of Polyurea Elastomers
Polymers 2019, 11(5), 838; https://doi.org/10.3390/polym11050838 - 08 May 2019
Cited by 4
Abstract
Four linear polyurea elastomers synthesized from two different diisocyanates, two different chain extenders and a common aliphatic amine-terminated polyether were used as models to investigate the effects of both diisocyanate structure and aromatic disulfide chain extender on hard segmental packing and self-healing ability. [...] Read more.
Four linear polyurea elastomers synthesized from two different diisocyanates, two different chain extenders and a common aliphatic amine-terminated polyether were used as models to investigate the effects of both diisocyanate structure and aromatic disulfide chain extender on hard segmental packing and self-healing ability. Both direct investigation on hard segments and indirect investigation on chain mobility and soft segmental dynamics were carried out to compare the levels of hard segmental packing, leading to agreed conclusions that correlated well with the self-healing abilities of the polyureas. Both diisocyanate structure and disulfide bonds had significant effects on hard segmental packing and self-healing property. Diisocyanate structure had more pronounced effect than disulfide bonds. Bulky alicyclic isophorone diisocyanate (IPDI) resulted in looser hard segmental packing than linear aliphatic hexamethylene diisocyanate (HDI), whereas a disulfide chain extender also promoted self-healing ability through loosening of hard segmental packing compared to its C-C counterpart. The polyurea synthesized from IPDI and the disulfide chain extender exhibited the best self-healing ability among the four polyureas because it had the highest chain mobility ascribed to the loosest hard segmental packing. Therefore, a combination of bulky alicyclic diisocyanate and disulfide chain extender is recommended for the design of self-healing polyurea elastomers. Full article
(This article belongs to the Special Issue Polymer Structure and Property)
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