Applications of Spectroscopic Techniques for Polymer Nanocomposite Characterization

13 During past decades, spectroscopic techniques find wide range of applications ranging from 14 biological applications to the measurement of chemical composition and characterization of 15 variety of substances i.e., polymers, nanocomposites etc. Nanocomposites are emerging and 16 growing materials having wide variety of uses. To study the characteristic properties, 17 characterize, and development of new materials using polymer nanocomposites, several 18 molecular characterization techniques are available and are in use today. Principle objective 19 of this review is to summarize the knowledge in current characterization techniques and to 20 study the applications of fluorescence, solid-state nuclear magnetic resonance (NMR), 21 infrared, besides Raman molecular characterization techniques for characterization of 22 polymers, filler, and composites. Fluorescence technique did not provide detailed analysis of 23 materials while solid-state NMR spectroscopy determine silanol hydroxyl groups at the silica 24 exterior in addition to their interactions with polymer and polymer-filler interfacial interactions 25 (via relaxation time). For characterization of various kinds of functional groups in polymer/ 26 fillers, infrared spectroscopy employed. While Raman spectroscopy finds extensive 27 applications for analysis of carbon-based materials. Novelty of this review is that till yet very 28 few review papers have been published which briefly describe all these mentioned techniques 29 along their applications in a very simple and an effective way. Infrared spectroscopy: this analysis technique widely used for material characterization via bands/ peaks specific for each functional group of the polymer. Raman spectroscopy: This technique finds extensive applications for characterization of carbon-based materials via 41 resonance-enhanced scattering effects. and nanocomposite polymer), relaxation period shows the probable two component decay. From results, it was found that in case of pure polymer, longer component has direct relationship with temperature and motion of polymer chains has direct relation with temperature. While in case of nanocomposite, temperature has less influence on chains mobility as compared to unadulterated polymer. The cause of this constrained motion is the interaction of filler with polymer chains leading to restricted motion of polymer chains [52]. owing to SBR phenyl parts (at strong MWCNT bands) while bands owing to vinyl parts are strong only as soon as MWCNTs are weak. Results indicate that alteration in orientation of phenyl rings with π - π interactions amongst polymer chains as well as MWCNTs is responsible for modification in local distribution of polymer chains [93]. Polymer-metal are used in the same way as surface-enhanced Raman scattering (SERS) substrates [96], is defined as molecular spectroscopic technique which increases Raman intensity of on irregular metal or finds upsurge in Raman Raman an in charge shifting nanoparticles graphene on the way to graphene-mediated surface-enhanced Raman scattering


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Nanomaterials i.e., spheres, sheets, as well as rods etc. spread in polymer materials found numerous applications and 44 study in rubber nanocomposites owing to their improved mechanical, electrical besides thermal characteristics. When 45 these filler elements are spread inside polymer matrix, it resulted in the extraordinary interfacial area amongst organic 46 and inorganic phases and interfacial connections amongst these two phases (governs the level of matrix strengthening) 47 [1] , [2].

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As compared to traditional carbon black, carbon nanomaterials, such as carbon nanotubes, graphite or graphene possess 72 excellent electrical conductivity, mechanical power combined with high aspect ratios. Owing to these characteristics, they 73 are known as advanced reinforcing fillers for polymeric metrices. Exceptional structure (made up of cylinders of single 74 or additional graphene layers) of carbon nanotubes (CNTs) make it more useful carbon nanostructure [2]. A lot of work 75 has been performed on methods used for dispersal of CNTs within polymer matrix. Among them calendaring is widely 76 used way, its principle and calendaring mechanism is shown in 77 Fig. 1

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Above debate revealed that a complete understanding of the composite and its properties is required before their use 99 and, in this regard, molecular spectroscopy is supportive which offers molecular level characterization. This review article 100 focuses on uses of molecular spectroscopy such as fluorescence, solid-state NMR, infrared, as well as Raman

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Box 1| unique properties of polymer nanocomposites polymer matrix composites having fillers with at least one dimension less than 100 nm are known as polymer nanocomposites. These polymer nanocomposites are of great interest in modern's world owing to several reasons which include:  These polymer nanocomposites have extraordinary large interfacial area because of their small size as compared to that of traditional composites [36]. Additionally, nanoscale fillers possess characteristics different from that of bulk properties of the same raw material e.g., on reducing size of silicon nanoparticles band gap fluctuate which then particle's color    acceptor one is best defined by FRET mechanism. This energy transfer takes place via nonradiative dipole-dipole 120 coupling. FRET process is highly dependent on distance that is 1 to 10 nm between two molecules. This process is used 121 to study the nanofeatures at border of a polymer-filler system. They studied dispersal of the supporting phase with

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Solid-state NMR spectroscopy

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Sensitivity of NMR spectra along with relaxation factors to the polymer chains are the basis which form solid-state NMR 147 spectra as suitable spectra for study of polymer-filler interfaces. To distinguish polymer performance in interfacial section 148 from bulk, solid-state NMR spectra was applied. Formulae (transverse magnetization relaxation function) used to find 149 out two dissimilar spin-spin relaxation times, T2, linked to polymer in solid-state proton NMR studies is given below: Where; 2 is spin-spin relaxation time linked to polymer in the bulk while 2 is spin-spin relaxation time of 152 polymer present at interface and 0 is portion of mobile chains external to adsorption coating. Formulae employed to 153 find width of interfacial layer is given below: Where: ω is portion of polymer, which is immobilized, ϕ is volume portion of filler while R is radius of particles

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When Ag nanoparticles were added to Polyaniline/ diamond/ functionalized multi-walled carbon nanotubes on polypropylene along with clay particles using infrared spectroscopy and "the tilted film method". They concluded that 250 clay orientation was relatively high-level owing to high anisometric nature of that kind of filer as compared to those technique. An illustration of AFM-IR technique is given in Fig. 8 [74].

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Raman spectroscopy is one of the best significant practices meant for study of carbon-centered composites for reason that 274 these composites create solid, well defined bands even at their low concentration owing to resonance-enhanced Raman 275 scattering effects [76]. However, some factors such as strain, pressure, filler-filler as well as polymer-filler interactions,

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To overcome the drawbacks of conventional Raman spectroscopy tip-enhanced Raman spectroscopy (TERS) i.e.,

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grouping of both Raman spectroscopy plus scanning probe microscopy has been used to obtain nanoscale spatial

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57. Li W, Hou L, Chen Z. An NMR investigation of phase structure and chain dynamics in the polyethylene/montmorillonite nanocomposites.