Polymers

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18 pages, 3736 KiB

Open AccessArticle

Bovine Serum Albumin Effect on Collapsing PNIPAM Chains in Aqueous Solutions: Spin Label and Spin Probe Study

by Georgii A. Simenido, Ekaterina M. Zubanova, Evgenii A. Ksendzov, Sergei V. Kostjuk, Peter S. Timashev and Elena N. Golubeva

Polymers 2024, 16(10), 1335; https://doi.org/10.3390/polym16101335 - 9 May 2024

Viewed by 1019

Abstract

The influence of bovine serum albumin (BSA) on collapsing poly(N-isopropylacrylamide) (PNIPAM) chains was studied with turbidimetry and spin probe and spin label electron paramagnetic resonance spectroscopy. An increased ratio of collapsed chains in aqueous solutions in the narrow temperature region near [...] Read more.

The influence of bovine serum albumin (BSA) on collapsing poly(N-isopropylacrylamide) (PNIPAM) chains was studied with turbidimetry and spin probe and spin label electron paramagnetic resonance spectroscopy. An increased ratio of collapsed chains in aqueous solutions in the narrow temperature region near the LCST appeared in the presence of 2.5–10 wt% BSA. The spin probe EPR data indicate that the inner cavities of the BSA dimers are probably responsive to the capture of small hydrophobic or amphiphilic molecules, such as TEMPO nitroxyl radical. The observed features of the structure and dynamics of inhomogeneities of aqueous PNIPAM-BSA solutions, including their mutual influence on the behavior of the polymer and protein below the LCST, should be considered when developing and investigating PNIPAM-based drug delivery systems. Full article

(This article belongs to the Special Issue Advanced Spectroscopy Methods in Polymer-Based Materials Analysis and Characterization)

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18 pages, 3842 KiB

Open AccessArticle

Exploring the Effect of Resins of Different Origin on the Structure, Dynamics and Curing Characteristics of SBR Compounds

by Michele Pierigé, Francesca Nardelli, Lucia Calucci, Mattia Cettolin, Luca Giannini, Andrea Causa, Francesca Martini and Marco Geppi

Polymers 2024, 16(6), 834; https://doi.org/10.3390/polym16060834 - 18 Mar 2024

Viewed by 1206

Abstract

The replacement of synthetic and petroleum-based ingredients with greener alternatives of natural origin is an imperative issue in rubber technology for the tire industry. In this study, a glycerin-esterified maleated rosin resin, derived from natural resources, is examined as a potential tackifier in [...] Read more.

The replacement of synthetic and petroleum-based ingredients with greener alternatives of natural origin is an imperative issue in rubber technology for the tire industry. In this study, a glycerin-esterified maleated rosin resin, derived from natural resources, is examined as a potential tackifier in styrene–butadiene rubber (SBR) formulations. A comparison is made with two synthetic resins commonly used as tackifiers in tire manufacturing: a petroleum-derived aromatic resin and a phenolic resin. Specifically, this research investigates how these resins affect the structure, dynamics, and curing characteristics of SBR compounds, which are strictly related to the mechanical and technological properties of the final products. Moving die rheometer and equilibrium swelling experiments are employed to analyze vulcanization kinetics and crosslink density, which are differently influenced by the different resins. Information on the polymer–resin compatibility is gained by differential scanning calorimetry and dynamo-mechanical analysis, while solid-state NMR methods offer insights into the structure and dynamics of both cured and uncured SBR compounds at the molecular level. Overall, our analysis shows that the resin of vegetal origin has a comparable impact on the SBR compound to that observed for the synthetic resins and could be further tested for industrial applications. Full article

(This article belongs to the Special Issue Advanced Spectroscopy Methods in Polymer-Based Materials Analysis and Characterization)

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12 pages, 1821 KiB

Open AccessArticle

Effect of Polymer Composition on the Optical Properties of a New Aggregation-Induced Emission Fluorophore: A Combined Experimental and Computational Approach

by Alberto Picchi, Qinfan Wang, Francesco Ventura, Cosimo Micheletti, Jesse Heijkoop, Francesco Picchioni, Ilaria Ciofini, Carlo Adamo and Andrea Pucci

Polymers 2023, 15(17), 3530; https://doi.org/10.3390/polym15173530 - 24 Aug 2023

Viewed by 1711

Abstract

Nowadays, fluorophores with a tetraphenylethylene (TPE) core are considered interesting due to the aggregation-induced emission (AIE) behavior that enables their effective use in polymer films. We propose a novel TPE fluorophore (TPE-BPAN) bearing two dimethylamino push and a 4-biphenylacetonitrile pull moieties [...] Read more.

Nowadays, fluorophores with a tetraphenylethylene (TPE) core are considered interesting due to the aggregation-induced emission (AIE) behavior that enables their effective use in polymer films. We propose a novel TPE fluorophore (TPE-BPAN) bearing two dimethylamino push and a 4-biphenylacetonitrile pull moieties with the typical AIE characteristics in solution and in the solid state, as rationalized by DFT calculations. Five different host polymer matrices with different polarity have been selected: two homopolymers of poly(methylmethacrylate) (PMMA) and poly(cyclohexyl methacrylate) (PCHMA) and three copolymers at different compositions (P(MMA-co-CHMA) 75:25, 50:50, and 25:75 mol%). The less polar comonomer of CHMA appeared to enhance TPE-BPAN emission with the highest quantum yield (QY) of about 40% measured in P(MMA-co-CHMA) 75:25. Further reduction in polymer polarity lowered QY and decreased the film stability and adhesion to the glass surface. LSC performances were not significantly affected by the matrix’s polarity and resulted in around one-third of the state-of-the-art due to the reduced QY of TPE-BPAN. The theoretical investigation based on density functional theory (DFT) calculations clarified the origin of the observed AIE and the role played by the environment in modulating the photophysical behavior. Full article

(This article belongs to the Special Issue Advanced Spectroscopy Methods in Polymer-Based Materials Analysis and Characterization)

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7 pages, 1966 KiB

Open AccessCommunication

Assessing the Quality of Oxygen Plasma Focused Ion Beam (O-PFIB) Etching on Polypropylene Surfaces Using Secondary Electron Hyperspectral Imaging

by Nicholas T. H. Farr, Maciej Pasniewski and Alex de Marco

Polymers 2023, 15(15), 3247; https://doi.org/10.3390/polym15153247 - 30 Jul 2023

Viewed by 1320

Abstract

The development of Focused Ion Beam–Scanning Electron Microscopy (FIB-SEM) systems has provided significant advances in the processing and characterization of polymers. A fundamental understanding of ion–sample interactions is still missing despite FIB-SEM being routinely applied in microstructural analyses of polymers. This study applies [...] Read more.

The development of Focused Ion Beam–Scanning Electron Microscopy (FIB-SEM) systems has provided significant advances in the processing and characterization of polymers. A fundamental understanding of ion–sample interactions is still missing despite FIB-SEM being routinely applied in microstructural analyses of polymers. This study applies Secondary Electron Hyperspectral Imaging to reveal oxygen and xenon plasma FIB interactions on the surface of a polymer (in this instance, polypropylene). Secondary Electron Hyperspectral Imaging (SEHI) is a technique housed within the SEM chamber that exhibits multiscale surface sensitivity with a high spatial resolution and the ability to identify carbon bonding present using low beam energies without requiring an Ultra High Vacuum (UHV). SEHI is made possible through the use of through-the-lens detectors (TLDs) to provide a low-pass SE collection of low primary electron beam energies and currents. SE images acquired over the same region of interest from different energy ranges are plotted to produce an SE spectrum. The data provided in this study provide evidence of SEHI’s ability to be a valuable tool in the characterization of polymer surfaces post-PFIB etching, allowing for insights into both tailoring polymer processing FIB parameters and SEHI’s ability to be used to monitor serial FIB polymer surfaces in situ. Full article

(This article belongs to the Special Issue Advanced Spectroscopy Methods in Polymer-Based Materials Analysis and Characterization)

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17 pages, 3475 KiB

Open AccessArticle

Advanced Particle Size Analysis in High-Solid-Content Polymer Dispersions Using Photon Density Wave Spectroscopy

by Stephanie Schlappa, Lena Bressel, Oliver Reich and Marvin Münzberg

Polymers 2023, 15(15), 3181; https://doi.org/10.3390/polym15153181 - 26 Jul 2023

Cited by 5 | Viewed by 1635

Abstract

High-solid-content polystyrene and polyvinyl acetate dispersions of polymer particles with a 50 nm to 500 nm mean particle diameter and 12–55% (w/w) solid content have been produced via emulsion polymerization and characterized regarding their optical and physical properties. Both [...] Read more.

High-solid-content polystyrene and polyvinyl acetate dispersions of polymer particles with a 50 nm to 500 nm mean particle diameter and 12–55% (w/w) solid content have been produced via emulsion polymerization and characterized regarding their optical and physical properties. Both systems have been analyzed with common particle-size-measuring techniques like dynamic light scattering (DLS) and static light scattering (SLS) and compared to inline particle size distribution (PSD) measurements via photon density wave (PDW) spectroscopy in undiluted samples. It is shown that particle size measurements of undiluted polystyrene dispersions are in good agreement between analysis methods. However, for polyvinyl acetate particles, size determination is challenging due to bound water in the produced polymer. For the first time, water-swelling factors were determined via an iterative approach of PDW spectroscopy error (Χ²) minimization. It is shown that water-swollen particles can be analyzed in high-solid-content solutions and their physical properties can be assumed to determine the refractive index, density, and volume fraction in dispersion. It was found that assumed water swelling improved the reduced scattering coefficient fit by PDW spectroscopy by up to ten times and particle size determination was refined and enabled. Particle size analysis of the water-swollen particles agreed well with offline-based state-of-the-art techniques. Full article

(This article belongs to the Special Issue Advanced Spectroscopy Methods in Polymer-Based Materials Analysis and Characterization)

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21 pages, 5124 KiB

Open AccessArticle

Multi-Spectroscopic Characterization of MgO/Nylon (6/6) Polymer: Evaluating the Potential of LIBS and Statistical Methods

by Amir Fayyaz, Haroon Asghar, Muhammad Waqas, Asif Kamal, Wedad A. Al-Onazi and Amal M. Al-Mohaimeed

Polymers 2023, 15(15), 3156; https://doi.org/10.3390/polym15153156 - 25 Jul 2023

Cited by 3 | Viewed by 3532

Abstract

The potential of using laser-induced breakdown spectroscopy (LIBS) in combination with various other spectroscopic and statistical methods was assessed for characterizing pure and MgO-doped nylon (6/6) organic polymer samples. The pure samples, obtained through a polycondensation chemical technique, were artificially doped with MgO [...] Read more.

The potential of using laser-induced breakdown spectroscopy (LIBS) in combination with various other spectroscopic and statistical methods was assessed for characterizing pure and MgO-doped nylon (6/6) organic polymer samples. The pure samples, obtained through a polycondensation chemical technique, were artificially doped with MgO prior to analysis for comparative purposes. These artificially doped samples served as crucial reference materials for comparative analysis and reference purposes. The LIBS studies were performed under local thermodynamic equilibrium (LTE) and optically thin plasma conditions. To assess the structural crystallinity of the nylon (6/6) polymer samples, X-ray diffraction (XRD) analysis, and Fourier transform infrared (FTIR) spectroscopy were employed to detect functional groups such as N-H, C-H, and C-N in the adsorbent polyamide nylon sample. Additionally, diffuse reflectance spectroscopy (DRS) analysis was conducted to investigate the effects of doping and temperature on the band gap and material reflectance across different sample temperatures. Chemical compositional analysis was performed using X-ray photoelectron spectroscopy (XPS) with the carbon C1s peak at 248.8 eV serving as a reference for spectrum calibration, along with energy-dispersive X-ray (EDX) analysis, which demonstrated good agreement between the techniques. To validate the different methodologies, the results obtained from CF-LIBS and EDX were compared with those from the standard inductively coupled plasma mass spectrometry (ICP-MS) technique. Finally, for classification analysis, principal component analysis (PCA) was applied to the LIBS spectral data at different sample temperatures (25 °C, 125 °C, 225 °C, and 325 °C). The analyses demonstrated that the combination of LIBS with PCA, along with other methods, presents a robust technique for polymer characterization. Full article

(This article belongs to the Special Issue Advanced Spectroscopy Methods in Polymer-Based Materials Analysis and Characterization)

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17 pages, 976 KiB

Open AccessArticle

Combining Experimental and Theoretical Tools to Probe Radio-Oxidation Products in Polyethylene

by Muriel Ferry, Yunho Ahn, Florian Le Dantec, Yvette Ngono and Guido Roma

Polymers 2023, 15(6), 1537; https://doi.org/10.3390/polym15061537 - 20 Mar 2023

Cited by 2 | Viewed by 1340

Abstract

Polyethylene is one of the most used polymers in a variety of sectors. A typical technique used to assess aging is infrared spectroscopy. Under oxidation, the region of the spectrum that is most studied is the one containing the carbonyl signature. However, various [...] Read more.

Polyethylene is one of the most used polymers in a variety of sectors. A typical technique used to assess aging is infrared spectroscopy. Under oxidation, the region of the spectrum that is most studied is the one containing the carbonyl signature. However, various carbonyl groups contribute to the carbonyl peak: ketones, aldehydes, esters, lactones, carboxylic acids, and more. A usual procedure to quantify each of them is the deconvolution of experimental peaks based on experimental assignments of infrared bands. In this paper, we complement this procedure, applied to two polyethylene types, with extended density functional theory (DFT) calculations of infrared spectra, using a polyethylene model mimicking the main features of a semicrystalline polymer. We compare theoretical frequencies and infrared intensities with parameters extracted from the literature that are used to, eventually, estimate concentrations. We provide an alternative estimation entirely based on theoretical data, showing that DFT can be a valuable tool to analyze, or at least complement, experimental data to assess polymer aging. The comparison of different deconvolution procedures raises the question of the contribution of conjugated ketones in the global carbonyl buildup, as well as that of ketones/alcohols pairs, or the relative concentration of esters and aldehydes. Full article

(This article belongs to the Special Issue Advanced Spectroscopy Methods in Polymer-Based Materials Analysis and Characterization)

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Review

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24 pages, 4222 KiB

Open AccessReview

Probing the Free Volume in Polymers by Means of Positron Annihilation Lifetime Spectroscopy

by Giovanni Consolati, Dario Nichetti and Fiorenza Quasso

Polymers 2023, 15(14), 3128; https://doi.org/10.3390/polym15143128 - 23 Jul 2023

Cited by 8 | Viewed by 2792

Abstract

Positron annihilation lifetime spectroscopy (PALS) is a valuable technique to investigate defects in solids, such as vacancy clusters and grain boundaries in metals and alloys, as well as lattice imperfections in semiconductors. Positron spectroscopy is able to reveal the size, structure and concentration [...] Read more.

Positron annihilation lifetime spectroscopy (PALS) is a valuable technique to investigate defects in solids, such as vacancy clusters and grain boundaries in metals and alloys, as well as lattice imperfections in semiconductors. Positron spectroscopy is able to reveal the size, structure and concentration of vacancies with a sensitivity of 10⁻⁷. In the field of porous and amorphous systems, PALS can probe cavities in the range from a few tenths up to several tens of nm. In the case of polymers, PALS is one of the few techniques able to give information on the holes forming the free volume. This quantity, which cannot be measured with macroscopic techniques, is correlated to important mechanical, thermal, and transport properties of polymers. It can be deduced theoretically by applying suitable equations of state derived by cell models, and PALS supplies a quantitative measure of the free volume by probing the corresponding sub-nanometric holes. The system used is positronium (Ps), an unstable atom formed by a positron and an electron, whose lifetime can be related to the typical size of the holes. When analyzed in terms of continuous lifetimes, the positron annihilation spectrum allows one to gain insight into the distribution of the free volume holes, an almost unique feature of this technique. The present paper is an overview of PALS, addressed in particular to readers not familiar with this technique, with emphasis on the experimental aspects. After a general introduction on free volume, positronium, and the experimental apparatus needed to acquire the corresponding lifetime, some of the recent results obtained by various groups will be shown, highlighting the connections between the free volume as probed by PALS and structural properties of the investigated materials. Full article

(This article belongs to the Special Issue Advanced Spectroscopy Methods in Polymer-Based Materials Analysis and Characterization)

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