Macromolecular NanotechnologyTailoring of interfacial properties by ionic liquids in a fluorinated matrix based nanocomposites
Graphical abstract
Nanoscale structuration of lamellar silicates in a PVDF matrix after modification with perfluorinated imidazolium ionic liquid.
Introduction
For many years, research in the field of polymer/clay nanocomposites has been widely extended [1], [2]. The nanoscale of nanoplatelets leads to an increase of surface to volume ratio generating a very huge amount of interface. The success of nanofillers dispersion into polymer matrix implies the tailoring of interactions between fillers and matrix. The objective is to process organic–inorganic nanomaterials for which all the polymer matrix chains are in a confined configuration with the consequences on chain mobility and on final properties such as thermal [3], mechanical [4] and barrier properties [5].
Polyvinylidene fluoride (PVDF) is a polymer commonly used in electronic and chemical industries due to its excellent chemical, thermal stabilities and mechanical properties. From a morphology view, it has several crystalline forms, i.e. α, β, γ, and δ [6]. While the α form is the most commonly generated one; the β form is the subject of research attention due to its extensive dielectric and pyroelectric applications of PVDF materials. Several ways could be followed to obtain the β form; (i) the application of a strain [7], (ii) the use of an electric field [8], (iii) the growth from a PVDF solution, and (iv) the introduction of inorganic fillers [9], [10]. For this last route, the influence of the modified clays on the mechanical properties has been widely studied in the literature. It has been shown that the use of Cloisite® 6 A and 20 A [11], [12], i.e. clays modified by alkylammonium ions, promotes the formation of β phase and a significant increase in the storage modulus is obtained with fillers contents from 1.5 to 7 wt.%. Shah et al. [13] showed that the addition of Cloisite® 30B (5 wt.%) increases Young’s modulus of 40% and strain at break of 250%. However, the great disadvantage of these ammonium salts is their poor thermal stability as degradation starts from 180 °C [14], [15], [16], which is the temperature limit for processing clay-based PVDF nanocomposites from melt intercalation. Recently, a new alternative to conventional ammonium emerges gradually with the ionic liquids (ILs). In particular, the imidazolium and phosphonium salts are known to possess an excellent thermal stability [17]. Patro et al. [18] used phosphonium and pyridinium ionic liquids as intercalant agents and have achieved an increase of 50% and 150% for Young’s modulus and strain at break, respectively.
In this work, the interfacial interactions between the fluorinated matrix and the lamellar silicates, i.e. montmorillonite, were tailored from a relevant selection of own-synthesized ionic liquids. The selected ILs have either an alkyl chain (imidazolium and phosphonium) or a fluorinated one (imidazolium) to match the PVDF matrix nature. Then, the key role of interfacial interactions will be argued in terms of morphology, crystallinity and mechanical properties of nanocomposites based on layered silicates modified by these new surfactants like ILs.
Section snippets
Materials
A sodic montmorillonite, denoted Nanofil 757 (MMT), i.e. an aluminosilicate with intercalated sodium ions, was chosen as pristine clay. This one was provided by Süd Chemie Co. The Nanofil 757 has a cationic exchange capacity of 95 meq/100 g and can be described by the following formula Na0.65[Al,Fe]4Si8O20(OH)4. All chemicals necessary for the synthesis of ionic liquids, i.e. triphenylphosphine (95%), imidazole (99.5%), iodooctadecyl (95%), and all the solvents (toluene, sodium methanoate,
Thermal stability of ionic liquid modified montmorillonites
The thermal stability of organically modified montmorillonites was characterized by Thermogravimetric Analysis (TGA). Fig. 1 displays the evolution of the weight loss as a function of temperature performed on the three montmorillonites exchanged either with imidazolium and phosphonium cations functionalized with long alkyl chains or with imidazolium cation functionalized with perfluorinated chain (C12). The degradation temperatures of physically adsorbed and intercalated species determined by
Conclusion
In this work, phosphonium and imidazolium ionic liquids were used as interfacial agents to enhance the physico-chemical interactions within the matrix and to help the lamellar silicates intercalation in the polymer matrix. The compatibility brought by the cation is the key parameter that governs the interactions and generates an exfoliated morphology responsible for the excellent compromise between stiffness and failure behaviour. Thus, a better dispersion of clay nanolayers and a plasticizing
References (28)
- et al.
Prog Polym Sci
(2008) Eur Polym J
(2007)et al.Polymer
(2006)Adv Mater
(1996)- et al.
Mater Sci Eng A
(2008) - et al.
J Appl Phys
(1979) - et al.
Adv Mater
(2005) - et al.
J colloid Interface Sci
(2010) - et al.
Polymer
(2008) - et al.
J Adhes
(2002) - et al.
Chem Mater
(2002)
Polymer
Colloid Polym Sci
Prog Polym Sci
Chem Mater
Cited by (33)
Potential of epoxy coating containing ionic liquid as anti-corrosion coating: Evaluation of barrier properties
2024, Surface and Coatings TechnologyHigh voltage stable solid-state lithium battery based on the nano-conductor imbedded flexible hybrid solid electrolyte with hyper-ion conductivity and thermal, mechanical, and adhesive stability
2022, Chemical Engineering JournalCitation Excerpt :When the impedance was re-measured after 30 days of aging process without any special preservation, the cell assembled using PVA-g-PCA-60IL-5HTpca binder showed a negligible change (Fig. 5a-2). Meanwhile, that using PVDF showed a huge increase in resistance due to the phase transition of PVDF at the interface of HSE and cathode under the same conditions [33–35]. Based on the superiority of the multi-functional utilization, HTpca-imbedded PVA-g-PCA/IL binder obviously provided intimate interfacial contact with cathode material to fulfill more desirable electrochemical stability.
Protic ionic liquids/poly(vinylidene fluoride) composite membranes for fuel cell application
2020, Journal of Energy ChemistryHuman cytotoxicity and octanol/water partition coefficients of fluorinated ionic liquids
2019, ChemosphereCitation Excerpt :An increase of the fluorinated chain length from four to eight carbon atoms promotes an extreme decrease of the hydrophilicity (Po/w value from −0.603 to 0.406), as depicted in Fig. 4b. The reported trend abides by the results of several authors that indicate that the over methylation and fluorination of a compound enhances their solubility in lipophilic solvents (Livi et al., 2011; Jeschke, 2004; Finizio et al., 1997). In addition, Purser et al. reported that aromatic fluorination, perpolyfluorination and fluorination adjacent to atoms with π-bonds exponentially increases lipophilicity (Purser et al., 2008).
Phosphonium ionic liquid as interfacial agent of layered double hydroxide: Application to a pectin matrix
2018, Carbohydrate PolymersCitation Excerpt :For these reasons, thermostable ionic liquids such as imidazolium or phosphonium salts have been used as surfactants of clays such as montmorillonite or LDH leading to improvements in the final properties but also a better distribution of clay layers in the polymeric materials. In fact, the use of organically modified montmorillonites or LDHs can significantly increase the thermal, mechanical and water vapor barrier properties of polymer matrices (Livi, Duchet-Rumeau & Gérard, 2011; Livi, Duchet-Rumeau, & Gérard, 2014; Livi, Duchet-Rumeau, Pham & Gérard, 2010; Livi, Duchet-Rumeau, Pham & Gérard, 2011; Livi, Dufour, Gaumont & Levillain, 2013; Livi, Sar, Bugatti, Espuche & Duchet-Rumeau, 2014). Different authors such as Kredatusová et al., Soares et al. and Ha et al. have demonstrated that ILs can be used as interfacial agent of LDH.
Influence of ionic liquid-modified LDH on microwave-assisted polymerization of ε-caprolactone
2016, PolymerCitation Excerpt :Versatility of ILs, coming from their ability to be modified via cationic or anionic exchange, enables a wide variety of structure designs and thus the choice of material fully compatible with both the used nanofiller and chosen polymer phase. Therefore, their application as surfactant agents for improving nanofiller-polymer interfacial adhesion has been tested for various nanocomposites [6–8]. Recently, phosphonium ILs with decanoate and dodecylsulfonate anions have been proven suitable as surfactants for LDH, enabling preparation of LDH/polylactide nanocomposites with improved thermal, mechanical as well as water permeation properties [9].