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All issues / Volume 14 (2020) / Issue 3 (March)

Hydrogels and bionanocomposites from peptide self-assembly
J. Puiggali
Vol. 14., No.3., Pages 205-205, 2020
DOI: 10.3144/expresspolymlett.2020.17
This is an editorial article. It has no abstract.
Strain rate effect and micro-buckling behavior of anisotropy macromolecular separator for lithium-ion battery
W. Q. Hao, J. M. Xie, X. Zhang, P. Wang, F. H. Wang
Vol. 14., No.3., Pages 206-219, 2020
DOI: 10.3144/expresspolymlett.2020.18
High tensile strength and good toughness play an important role in improving the mechanical performance of separator films, such as resistance to external force, service life and so on. In the present research, the strain rate effect and microbuckling behavior of two types of anisotropic separators for lithium-ion battery (LIB) under different strain rates are investigated. The results conclude that the anisotropy effect and strain rate effect are displayed obviously along the machine direction (MD), diagonal direction (DD) and transverse direction (TD). The constitutive relationship with a strain rate of anisotropicmacromolecular separator for LIB is ln{ε/σ-1/(E0[1+λ1(lnε.-lnε.0)])}=κlnε-lnE0-ln[1+λ1(lnε.-lnε.0)]. The separator has high tensile strength along MD and good toughness along DD and TD. The maximum error of strain rate strengthening coefficient λ1 and λ/ about the material parameter is less than 15%. Finally, the critical stress σx,crit = –Ekπ2(t/B)2/12(1 – μ2) characterizing the micro-buckling behavior of macromolecular separators are proposed and discussed. The critical stress error rates are approximately Error = 2–7% compared with experimental results. This research provides guidance to improve the mechanical property of anisotropic separator and addresses the safety of LIB.
Low melting point, high thermal stable branched benzoxazines resin derived from mixed-substituted phosphazene core
H-X. Ma, J-J. Qiu, C-M. Liu
Vol. 14., No.3., Pages 220-234, 2020
DOI: 10.3144/expresspolymlett.2020.19
Six fluorine-containing, mix-substituted phosphazene-based branched benzoxazine monomers with a low melting point were successfully prepared and their chemical structures were verified by 1H, 13C, 31P and 19F nuclear magnetic resonance (NMR). These branched benzoxazine resins underwent thermal ring-opening polymerization to form cured polymers with high thermal stability both in N2 atmosphere and in air. The co-substituents, both m-CF3PhOH and p-CF3PhOH, imposed significant effects on processing, thermal, and surface properties of corresponding polybenzoxazines. Non-isothermal differential scanning calorimetry (DSC) under diverse heating rates was adopted to investigate the curing kinetics and determine the activation energy of polymerization. DSC results indicate that the m-CF3PhO–/p-CF3PhO– groups have the potential to lower ring-opening polymerization temperature. Glass transition temperatures (Tgs) of polybenzoxazines derived from p-CF3PhOH are higher than that of polymers derived from m-CF3PhOH due to different steric hindrance and crosslinking density. More interesting, all polybenzoxazines show relatively high dielectric constant but exhibit low dielectric loss at ambient temperature.
Dually-functional riboflavin macromolecule as a supramolecular initiator and reducing agent in temporally-controlled low ppm ATRP
I. Zaborniak, P. Chmielarz
Vol. 14., No.3., Pages 235-247, 2020
DOI: 10.3144/expresspolymlett.2020.20
A novel supramolecular riboflavin-inspired macroinitiator was prepared for the first time by transesterification methodology and used as the multifunctional vitamin-B2 core to synthesize PBA brushes using different low ppm atom transfer radical polymerization (ATRP) approaches. Firstly the macromolecular initiator was successfully applied as a dually-functional structure, which simultaneously acts as a reducing agent in activator regeneration by electron transfer (ARGET) ATRP. Subsequently simplified electrochemically mediated ATRP of BA with different conditions was carried out for the preparation of well-defined riboflavin-based polymer brushes. Polymerizations were characterized in a well-controlled manner, affording polymers with a narrow dispersity (Ð = 1.22–1.25). Four-arms polymers were also received by an approach never described before – temporally-controlled multi-step seATRP under constant current conditions, giving precisely-defined polymer brushes (Ð = 1.26) with preserved chain-end functionality (DCF < 1%), despite stopping and restarting the polymerization. The solvolysis results indicate that all chains grow to equal lengths (Ð < 1.17), which shows the precisely controlled characteristic of seATRP. 1H NMR analysis confirms the formation of new vitamin B2-inspired polymers. In connection with the preserved riboflavin functionality and additional functional chains, these innovative macromolecules may find applications, e.g. as drug delivery systems.
Click-cross-linked, doxorubicin-loaded hydrogels based on poly(styrene-alt-maleic anhydride)
D. S. B. Anugrah, M. P. Patil, X. Li, C. M. Q. Le, K. Ramesh, G-D. Kim, K. Hyun, K. T. Lim
Vol. 14., No.3., Pages 248-260, 2020
DOI: 10.3144/expresspolymlett.2020.21
A new type of hydrogels based on poly(styrene-alt-maleic anhydride) (PSMA) was prepared via Diels-Alder click chemistry. The formulations consisting of tetrazine-functionalized PSMA as a multi-clickable polymer and norbornene-terminated poly(ethylene glycol) (PEG) as a polymeric cross-linker were used as precursors to give ultrafast hydrogels with controlled structures. The hydrogels formed within several minutes under a physiological condition without any catalyst, and their storage modulus (G′) values were in the range 0.3–1.7 kPa suitable for bio-applications. The pore structure and the release profile of doxorubicin hydrochloride (DOX・HCl) of the hydrogels could be manipulated by the molecular weight of PEG. The precursors exhibited practically no depressing effect of the normal HEK293 growth, while the DOX・HCl-loaded hydrogel presented significant anticancer activity towards HeLa cells. The results suggested this biocompatible hydrogel as a potential injectable drug depot for tumor sites.
Effect of filler and blending with SBR and NR on thermally induced crystallization of high-cis BR as evaluated by dynamic mechanical analysis
M. Wunde, M. Klueppel
Vol. 14., No.3., Pages 261-271, 2020
DOI: 10.3144/expresspolymlett.2020.22
The effect of thermally induced crystallization of high-cis polybutadiene (BR) on dynamic mechanical spectra is analyzed under different heating and cooling conditions. It is studied how the addition of carbon black and the blending with styrene-butadiene rubber (SBR) and natural rubber (NR) is affecting the crystallization. For unfilled BR an increased heating rate after fast cooling delivers less crystallization demonstrating that crystal formation requires time. With rising carbon black (CB) loading, a pronounced increase of crystallization speed is found indicating that CB supports nucleation and growth of BR crystals. In BR/SBR blends, which are detected as a single phase in dynamic mechanical spectra, crystallization is reduced for low SBR amounts and seems to disappear totally for 50/50 blends. In blends of BR, SBR, and NR the filler distribution is determined by comparing the peak heights in the loss modulus G″ of unfilled and filled compounds. The filler located in each phase is determined from the increase of the peak height corresponding to the respective phase. It is found that the filler is mainly located in the NR phase.
Synthesis, properties and enzymatic biodegradation behavior of fluorinated poly(ε-caprolactone)s
G. Acik
Vol. 14., No.3., Pages 272-280, 2020
DOI: 10.3144/expresspolymlett.2020.23
This study reports on the synthesis of new fluoro functionalized poly(ε-caprolactone)s (F-PCLs) via ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) for different time intervals (24 and 48 h.) by using 2,2,3,3,4,4,5,5-octafluoro-1-pentanol (OFP) as an initiator. The structure and properties of F-PCLs are investigated by Fourier-transform infrared (FT-IR), proton and fluorine 19 nuclear magnetic resonance (1H-NMR and 19F-NMR) spectroscopies, gel permeation chromatography (GPC), energy dispersive scanning electron microscopy (SEM-EDS), atomic force microscopy (AFM), water contact angle (WCA) measurements, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Enzymatic degradation experiments are also conducted to study the biodegradation behavior of terminal F-PCLs. Experimental observations obtained by 1H-NMR, 19F-NMR and GPC indicate that higher reaction time leads to the formation of higher fluorinated repeating units in F-PCLs. This observation is confirmed by results of SEM-EDS, AFM, WCA, DSC and TGA analyses, respectively. Based on the biodegradability study of F-PCLs in degradation solutions in the presence and absence of porcine pancreatic lipase, it can observed that utilization of more extended time in the ROP reaction medium decreases the biodegradation of resulting polymer. With the obtained features, biodegradable F-PCLs might have potential applications, particularly in the fields of drug delivery and tissue engineering, requiring improved thermal but lower wettability properties.
Facile design of heat-triggered shape memory ethylene-acrylic acid copolymer/chloroprene rubber thermoplastic vulcanizates
F. F. Liu, Y. T. Sun, Z. B. Wang
Vol. 14., No.3., Pages 281-293, 2020
DOI: 10.3144/expresspolymlett.2020.24
Stimuli-responsive shape-memory ethylene-acrylic acid copolymer (EAA)/chloroprene rubber (CR) thermoplastic vulcanizates (TPVs) were prepared via dynamic vulcanization. Meanwhile, a simple and effective strategy was designed to achieve rapidly reconfigurable shape fixity and shape recovery for a heat-triggered shape-memory polymer (HSMP), which was derived from a typical sea-island structured EAA/CR TPVs. Field emission scanning electron microscopy (FE-SEM) showed the average diameter of CR particles in EAA/CR TPVs was 3~8 µm. In this work, the mechanical properties results showed that the EAA/CR TPV had high tensile strength, indicating a strong interface interaction between EAA and CR, which would inevitably improve the shape recovery (SR) and shape fixing (SF) ability of TPVs. This HSMP exhibited the surprising shape-memory property (shape fixity ratio ~97%, shape recovery ratio ~95%, and fast recovery speed <30 s). The dynamic mechanical behavior and stress relaxation behavior of EAA/CR TPVs were characterized, and the results demonstrated that the high modulus value supported the improvement of SF ratios, and with the decrease continuously of EAA in the EAA/CR TPVs, the low-stress relaxation ratio stimulated the improvement of SR ratios of the EAA/CR TPVs. This novel HSMP expected to open up a wide range of potential applications in smart devices.
Published by:

Budapest University of Technology and Economics,
Faculty of Mechanical Engineering, Department of Polymer Engineering