Polymer layered silicate nanocomposites (PLSNs) made of montmorillonite (MMT) nanosheets and poly(methyl acrylate) (PMA) are synthesized and systematically characterized. MMT is first modified with a surface‐bound monomer and then functionalized with PMA via radical addition–fragmentation chain transfer (RAFT) polymerization using a grafting through approach. PMA‐modified MMT nanosheets with grafted polymer chains of variable length are obtained. The successful surface modification is demonstrated by near‐field scanning optical microscopy, thermogravimetric analysis, attenuated total reflection Fourier transform infrared spectroscopy, small‐angle X‐ray scattering, and size‐exclusion chromatography. The mechanical properties of various nanocomposites are evaluated via tensile testing. It can be shown that the mechanical properties (Young's modulus, tensile strength, toughness, and ductility) of these PLSNs can be fully controlled by using two major strategies, i.e., by the variation of the overall content of polymer‐modified MMT and by the variation of the chain length of the surface‐grafted polymer.
both polystyrene-and poly(methyl methacrylate)-grafted silica nanoparticles and produced a material consisting only of particles and surface-tethered polymer chains. They could observe a dependency of the materials Young's modulus, fracture toughness, and hardness on the degree of polymerization (DP) of the grafted polymer. [8] Crucial for the successful preparation of such materials is the presence of interactions between different particles through entanglement of polymer chains bound to different particles. This is given if the chains are long enough to entangle with each other or if the chains are cross-linked. [6] Additionally, research strives for achieving an order of the particles as it is hoped to produce materials with, for example, superior optical properties. [6,8] One naturally occurring "matrix-free" material with exceptional mechanical properties is nacre, which consists of 95 vol.-% of aragonite platelets and 5 vol.-% of organic biopoly mer. [9] They form a composite with a "brick-and-mortar"-like structure, which exhibits exceptional mechanical properties. The Young's modulus is known to be up to 135 GPa accompanied by a fracture toughness of up to 1.8 MJ m −3 . These properties can be assigned to the unique structure of this special material. [9,10] A biomimetic approach to produce a similar synthetic material is the use of layered nanoparticles, substituting the aragonite, and synthetic organic molecules to replace the natural biopolymer. Different nanoparticles, such as graphene oxide, [11,12] Al 2 O 3 platelets, [13] or nanoclays [4,10,14,15] have been used so far.In this publication, we report the successful preparation of a nacre-like material using montmorillonite (MMT) nanosheets and for the first time PMA to form self-standing films and explore new strategies to tailor their mechanical properties by modifying the polymer functionalization of the platelets. Using the soft and ductile PMA allows for the formation of nanocomposites that show an exceptionally high modulus and tensile strength without being brittle. The mechanical properties of the novel material are further enhanced by cross-linking of the surface-grafted polymer, which is either achieved via radical addition-fragmentation chain transfer (RAFT) star-polymerization upon the platelet surface or via introducing hydrogen-bonding moieties to the surface-grafted polymer. Matrix-free nanocomposite films of poly(methyl acrylate) (PMA) and montmorillonite (MMT) nanosheets that imitate the microscopic structure of nacre are developed and their mechanical properties are studied in detail via tensile testing. The exfoliated MMT nanosheets are grafted with PMA via a grafting-through radical addition-fragmentation chain transfer polymerization in presence of a surface-anchored ionic monomer. The mechanical properties are precisely tailored a) via the variation of the degree of polymerization of the surface-grafted polymer, illustrating the impact of chain entanglement and the MMT content on the performance of the material, and b) via cros...
Nanocomposites combine multiple favorable properties to achieve intriguing functionalities, but the formation of nanocomposites with only one constituent with the inclusion of multiple superior properties is still not known. Herein, novel self-compounded nanocomposite membranes from one single polymercellulose cinnamate (CCi)with multiple outstanding properties are reported. The self-compounded membranes contain two distinct morphologies as CCi nanoparticles (CCi-NPs) and a CCi polymer matrix, while CCi-NPs are either firmly embedded in the CCi matrix or fused with adjacent CCi-NPs. The unique self-compounded nanostructure endows the membranes with a tensile strength of 94 MPa and Youngʼs modulus of 3.1 GPa. The water vapor permeability, oxygen permeability, and oil permeability reach as low as (0.94 ± 0.03) × 10–11 g m–1 s–1 Pa–1, (8.48 ± 2.39) ×10–13 cm3·cm/cm2·s·cmHg, and 0.008 ± 0.003 g mm m–2 day–1, respectively. Moreover, self-compounded CCi nanocomposite membranes also demonstrate UV-shielding and photothermal conversion properties. UVB and UVC light are entirely blocked, while UVA light is partly blocked. The temperature increases from room temperature to 120 °C within 1 min under UV irradiation. In addition, CCi membranes also show remarkable thermal and humidity resistance. Based on these outstanding properties, CCi membranes are applied as food packaging materials. This work offers a new avenue to construct nanocomposites with multiple superior properties from one constituent, which is promising for diverse applications.
Low-density polyethylene (LDPE) foils were coated with a thin film of polymer-grafted Montmorillonite (MMT) nanosheets, which form a barrier against gas diffusion due to their unique brick-and-mortar arrangement. The MMT nanosheets were grafted with poly(methyl acrylate) (PMA), a soft and flexible polymer. Already very thin films of this nanocomposite could reduce gas permeability significantly. The impact of the topology of the surface-grafted polymer on gas permeability was also studied. It was found that grafting MMT nanosheets with a mixture of star-shaped and linear PMA and with PMA that is cross-linked via hydrogen bonds further decrease gas permeability. The presented strategy is quick and simple and allows for the easy formation of effective gas barrier coatings for LDPE foils, as used in food packaging.
Polymer-nanocomposites based on sustainable fillers are integral to the development of modern high-performance materials. Consequently, the successful preparation of Montmorillonite (MMT)polymer-nanocomposites with tailorable mechanical properties via surface grafting of RAFT polymers was established. Strategies to precisely tune the properties of filler-matrix and matrix-free composites were developed and characterized via tensile testing. The possible application of these approaches for the synthesis composites with enhanced gas barrier properties was explored.The naturally occurring layered silicate MMT was modified with an ionic monomer for radical polymerization via an ion exchange procedure and subsequently employed in a grafting through RAFTpolymerization of methyl acrylate. The successful surface modification with monomer and polymer was demonstrated with a variety of methods. Thermogravimetric analysis (TGA) and elemental analysis (EA) both showed a significant increase of organic content after modification. attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy was used to demonstrate the presence of all components (MMT, surface grafted monomer, and polymer) in the resulting composites. scanning near-field optical microscopy (s-SNOM) allowed for the proof that a significant amount of polymer can be immobilized at the surface while any unbound polymer can be separated from the sample. Hence, the production 3.1. Methods used throughout this thesis S Z S R Scheme 3.1: Schematic structure of a RAFT agent. 42 Scheme 3.2: General mechanism of a RAFT polymerization. 42 Blue balls represent monomer units.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.