Review
Ultrasound assisted in situ emulsion polymerization for polymer nanocomposite: A review

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Highlights

  • This review covers an ultrasound assisted synthesis of polymer nanocomposites using in situ emulsion polymerization.

  • This technique helps in preparation of stable and finely dispersed polymer nanocomposite.

  • Recent developments in the preparation of core–shell polymer nanocomposites were reported.

Abstract

This review covers an ultrasound assisted synthesis of polymer nanocomposites using in situ emulsion polymerization. First of all, surface modification of core nanoparticles with a coupling agent and surfactant has been employed for the synthesis of core–shell polymer nanocomposites. In addition to application of ultrasound for the synthesis of core–shell polymer nanocomposites, due to its influential efficiency, sonochemistry has been extensively used not only as an aid of dispersion for inorganic nanoparticles and organo-clay, but also acts as an initiator to enhance polymerization rate for synthesis of polymer nanocomposites. In situ emulsion polymerization of hydrophobic monomers, such as methyl methacrylate, butyl acrylate, aniline, vinyl monomers and styrene, using surfactant and water soluble initiator were carried out for a synthesis of core–shell polymer nanocomposite. This technique assists in preparation of stable and finely dispersed polymer nanocomposite with the loading of inorganic particles up to 5 wt.%. Recent developments in the preparation of core–shell polymer nanocomposites using an ultrasound assisted method with their physical characteristics such as morphology, thermal, and rheological properties and their potential engineering applications have been discussed in this review.

Introduction

The first attempt to use of the ultrasound in enhancement of chemical reaction rates was reported by Richards, A.L. Loomis in 1927 [1]. Since then the use of ultrasound in the synthesis has attracted a lot of interest, in various fields of chemistry, materials science and chemical engineering [2], [3], [4]. Cavitation as a phenomenon was first identified and reported by Thornycroft and Barnaby in 1895 [5]. When more powerful ultrasound at a lower frequency is applied to a system, it is possible to produce the chemical changes as a result of acoustically generated cavitation. The generation of radicals takes place due to the extreme environment created by acoustic cavitation [6], [7]. In addition, the physical effect of the medium on the wave is referred to low power or high frequency ultrasound. The physical effect in the fields of nanomaterials like thermal heating, mass transfer, emulsification, and surface cleaning are induced by cavitation [8].

Application of sonochemistry in materials science and nanotechnology has been covered and reviewed by a several authors [2], [8], [9], [10], [11], [12]. Early reviews on nanostructured materials prepared using ultrasound radiation and applications of ultrasound to materials chemistry were carried out by Suslick and Price [2], [9]. Then the review on “Ultrasound assisted chemical processes” was carried out by Ashokkumar and Grieser [10]. This review highlighted the area of synthesis of the nanomaterials using ultrasound assisted technique. They have reviewed the use of ultrasound in homogeneous (radical and pyrolytic) and heterogeneous (synthesis of metal and semiconductor particles, complex molecules such as protein and polymers) reaction systems. Further, they have described the effect of ultrasound on leather processing, drug delivery, intraparticle collisions, precipitation stripping of rare earth oxalates and water treatment. The review on sonochemistry for the fabrication of nanomaterials has been carried out by Gedanken [8]. He has reviewed the work related to materials science and nanotechnology, in which it has been concluded that the sonochemical method of synthesis is superior over all other existing techniques. The topics reviewed were preparation of amorphous products, insertion of nanomaterials into mesoporous materials, deposition of nanoparticles on ceramic and polymeric surfaces and the formation of proteinaceous micro- and nanospheres using cavitation technique. The recent reviews [11], [12] reported the sonochemical fabrication of polymer nanocomposites and sonochemical synthesis of nanostructured materials such as carbon nanotubes (CNT), organophillic clay, and metal nanoparticles.

In the area of polymer science, due to the intense conditions generated by acoustic cavitation, ultrasound acts as an initiator by breaking chemical bonds of molecules and thus enhances the rate of polymerization. Cao et al. [13] have studied the radical generation mechanism in ultrasonically irradiated emulsion copolymerization of styrene in the presence of a cationic surfactant (methacryloxyethyl dodecydimethyl ammonium bromide, C12N+) without adding any chemical initiators. Under ultrasonic irradiation condition, C12N+ undergoes bond scission between the two alkyl and ionic group thus producing much more original radicals to initiate the emulsion polymerization. Teo et al. [14] have reported the miniemulsion polymerization of methacrylate monomers in the presence of ultrasound without the use of external initiator and at 30 °C (room temperature synthesis using cavitation). They have observed that these cavitation based polymerization reactions follow pseudo-first-order kinetics and further it has been reported that a radical enters the monomer droplet containing a growing radical will lead to pseudo-instantaneous termination. The mechanism for the preparation of polymer latex particles involved in sonochemical process is very similar to that of a conventional miniemulsion polymerization process. Ultrasonically initiated emulsion polymerization of methyl methacrylate [14], [15], [16], [17], [18], [19], [20], styrene [17], [18], [21], [22], [23], [24], n-butyl methacrylate [25], n-butyl acrylate [19], [22], [26] were also studied. The rate of polymerization of methacrylate monomers [14] is strongly dependent on the temperature, vapor pressure and hydrophobicity of monomer and ultrasonic intensity, which were the important findings reported by Teo et al. [14].

For the preparation of polymer nanocomposites either organic molecules or inorganic particles can be encapsulated into inorganic materials or organic polymer latex, which could be accomplished by applying cavitation during the polymerization process. There have been several research articles which describe the preparation of polymer nanocomposite by conventional in situ emulsion polymerization, but attempt was not successful in making complete encapsulation [27], [28], [29], [30], [31], [32], [33]. Recently, numbers of attempts were made by the researchers in the preparation of polymer nanocomposites latexes using ultrasonically initiated in situ emulsion polymerization [34], [35], [36], [37], [38], [39], [40], [41], [42], [43], [44], [45], [46]. This ultrasound assisted in situ emulsion polymerization technique provides an effective way of synthesizing finely dispersed inorganic particles in polymer latex along with many advantages such as higher polymerization rate, narrow molecular weight and particle size distribution, higher monomer conversion and no or small amount of external initiator requirement compared to convention in situ emulsion polymerization [34], [35], [36], [37], [38], [39], [40], [41], [42], [43], [44], [45], [46]. Fillers, such as titanium dioxide, calcium carbonate, clays, several oxides and metal particles were encapsulated by means of ultrasound assisted in situ emulsion polymerization [34], [35], [36], [37], [38], [39], [40], [41], [42], [43], [44], [45], [46]. Addition of untreated inorganic particles during emulsion polymerization makes system unstable and leads to agglomeration of particles. Hence, functionalization of inorganic fillers plays an important role during the encapsulation process. Surface modification of an inorganic particle with an organic molecule is one of the ways to reduce its surface energy and to increase its compatibility with the organic polymer matrix. The surface modification has been extensively carried out using different organic modifiers and surfactants, e.g. silane coupling agents, titanate coupling agents, or stearic acid, myristic acid, etc. [47], [48], [49], [50], [51].

Section snippets

Ultrasound assisted emulsion polymerization

It is well known that for emulsion polymerization, hydrophobic monomer, emulsifier and hydrophilic initiator are the main constituents could be used in the water phase (continuous phase). Polymers such as acrylonitrile butadiene styrene, polystyrene, poly-methyl methacrylate, etc. can be easily prepared via emulsion polymerization processes. These conventional emulsion polymerization processes have different disadvantages, e.g. high polydispersity of particles, and instability of colloidal

Polymer nanocomposites synthesis techniques and role of ultrasound in polymer nanocomposites preparation

Preparation of polymer nanocomposite from nano-inorganic additives and polymers has been accomplished by the means of surface encapsulation or surface grafting. Several methods have been implemented to synthesize polymer nanocomposites. Some of them are, suspension polymerization [58], [59] emulsion polymerization [60], intercalative polymerization [61], solution casting method [62], hybrid latex polymerization [63]. Improper dispersion of inorganic nanoparticles and weak bonding between

Types of polymer nanocomposites synthesized by ultrasound assisted in situ emulsion polymerization

Encapsulated polymer nanocomposites are intended to combine the best features of the organic and the inorganic compound. These hybrid particles can be defined as colloidal particles that include both organic and inorganic compounds. These polymer nanocomposites can be prepared by (a) combining organic and inorganic components, (b) reacting organic and inorganic precursors, or (c) polymerizing in situ organic and/or inorganic precursors in the presence of their corresponding compound. An

Conclusions

The current development of polymer nanocomposites prepared by ultrasound assisted in situ emulsion polymerization with inorganic particles such as inorganic oxides, metal, magnetic particle, CNT and clay have been reviewed. In this ultrasonic irradiation not only initiate polymerization of monomers such as MMA, nBA, styrene, etc. at room temperature while inorganic nanoparticles/clay layers were dispersed at the nanoscale, but can also shorten the polymerization time and save the energy. Thus,

References (158)

  • X. Xie et al.

    Rheological and mechanical properties of PVC/CaCO3 nanocomposites prepared by in situ polymerization

    Polymer

    (2004)
  • O. Yilmaz et al.

    Preparation of stable acrylate/montmorillonite nanocomposite latex via in situ batch emulsion polymerization: effect of clay types

    Appl. Clay Sci.

    (2010)
  • C.G. Dobie et al.

    Surfactant-free emulsion polymerisation of methyl methacrylate and methyl acrylate using intensified processing methods

    Chem. Eng. Process.: Process. Intensif.

    (2010)
  • S. Liu et al.

    Core–shell magnesium hydroxide/polystyrene hybrid nanoparticles prepared by ultrasonic wave-assisted in-situ copolymerization

    Mater. Lett.

    (2009)
  • J. Jiang

    Ultrasonic-assisted synthesis of PMMA/Ni0.5Zn0.5Fe2O4 nanocomposite in mixed surfactant system

    Eur. Polym. J.

    (2007)
  • M. Sivakumar et al.

    A sonochemical method for the synthesis of polyaniline and Au–polyaniline composites using H2O2 for enhancing rate and yield

    Synth. Met.

    (2005)
  • G. Qiu et al.

    Polystyrene/Fe3O4 magnetic emulsion and nanocomposite prepared by ultrasonically initiated miniemulsion polymerization

    Ultrason. Sonochem.

    (2007)
  • J. Wang et al.

    Preparation of nanocomposite of polyaniline and gamma-zirconium phosphate (γ-ZrP) by power ultrasonic irradiation

    Mater. Res. Bull.

    (2003)
  • L.J. Borthakur et al.

    Development of core–shell nano composite of poly(styrene-co-methyl acrylate) and bentonite clay by ultra sonic assisted mini-emulsion polymerization

    Mater. Chem. Phys.

    (2010)
  • Z. Demjén et al.

    Interaction of silane coupling agents with CaCO3

    J. Colloid Interface Sci.

    (1997)
  • G.J. Price

    Recent developments in sonochemical polymerization

    Ultrason. Sonochem.

    (2003)
  • D. Kobayashi et al.

    Improvement of indirect ultrasonic irradiation method for intensification of emulsion polymerization process

    Chem. Eng. J.

    (2008)
  • M. Nie et al.

    Enhancement of ultrasonically initiated emulsion polymerization rate using aliphatic alcohols as hydroxyl radical scavengers

    Ultrason. Sonochem.

    (2008)
  • B.A. Bhanvase et al.

    Analysis of semibatch emulsion polymerization: role of ultrasound and initiator

    Ultrason. Sonochem.

    (2012)
  • P. Kruus

    Polymerization resulting from ultrasonic cavitation

    Ultrasonics

    (1983)
  • P. Liu et al.

    In situ radical transfer addition polymerization of styrene from silica nanoparticles

    Eur. Polym. J.

    (2004)
  • G. Chen et al.

    Preparation of polystyrene/graphite nanosheet composite

    Polymer

    (2003)
  • J. Li et al.

    Conductive graphite nanoplatelet/epoxy nanocomposites: effects of exfoliation and UV/ozone treatment of graphite

    Scr. Mater.

    (2005)
  • M.Z. Rong et al.

    Improvement of tensile properties of nano-SiO2/PP composites in relation to percolation mechanism

    Polymer

    (2001)
  • S.K. Swain et al.

    Effect of ultrasound on HDPE/clay nanocomposites: rheology, structure and properties

    Polymer

    (2007)
  • X.F. Ma et al.

    Preparation of polyaniline–TiO2 composite film with in situ polymerization approach and its gas-sensitivity at room temperature

    Mater. Chem. Phys.

    (2006)
  • B.G. Soares et al.

    The in situ polymerization of aniline in nitrile rubber

    Synth. Met.

    (2006)
  • J.L. Luna-Xavier et al.

    Synthesis and characterization of silica/poly(methyl methacrylate) nanocomposite latex particles through emulsion polymerization using a cationic azo initiator

    J. Colloid Interface Sci.

    (2002)
  • A.R. Mahdavian et al.

    Preparation of poly (styrene–methyl methacrylate)/SiO2 composite nanoparticles via emulsion polymerization. An investigation into the compatiblization

    Eur. Polym. J.

    (2007)
  • W. Wu et al.

    Study on in situ preparation of nano calcium carbonate/PMMA composite particles

    Mater. Lett.

    (2006)
  • X. Chen et al.

    Interfacial adhesion and mechanical properties of PMMA-coated CaCO3 nanoparticle reinforced PVC composites

    China Particuol.

    (2006)
  • X. Ma et al.

    Study on CaCO3/PMMA nanocomposite microspheres by soapless emulsion polymerization

    Colloids Surf. A

    (2008)
  • Y. Sheng et al.

    In situ preparation of CaCO3/polystyrene composite nanoparticles

    Mater. Lett.

    (2006)
  • W.T. Richards et al.

    The chemical effects of high frequency sound waves. I. A preliminary survey

    J. Am. Chem. Soc.

    (1927)
  • K.S. Suslick et al.

    Applications of ultrasound to materials chemistry

    Annu. Rev. Mater. Sci.

    (1999)
  • M. Blaskovicova et al.

    Synthesis and photochemistry of 1-iodocyclohexene: influence of ultrasound on ionic vs. radical behaviour

    Molecules

    (2007)
  • X.K. Wang et al.

    Sonochemical degradation kinetics of methyl violet in aqueous solutions

    Molecules

    (2003)
  • J. Thornycroft et al.

    Torpedo boat destroyers

    Proc. Inst. Civil Eng.

    (1895)
  • T.J. Mason et al.

    Sonochemistry: Theory, Applications and Uses of Ultrasound in Chemistry

    (1988)
  • T.J. Mason

    Sonochemistry The Uses of Ultrasound in Chemistry

    (1990)
  • K.S. Suslick et al.

    Nanostructured materials generated by high-intensity ultrasound: sonochemical synthesis and catalytic studies

    Chem. Mater.

    (1996)
  • M. Ashokkumar et al.

    Ultrasound assisted chemical processes

    Rev. Chem. Eng.

    (1999)
  • J.H. Bang et al.

    Applications of ultrasound to the synthesis of nanostructured materials

    Adv. Mater.

    (2010)
  • K. Zhang et al.

    Sonochemical preparation of polymer nanocomposites

    Molecules

    (2009)
  • C. Parra et al.

    Synthesis and characterization of poly(methyl methacrylate) obtained by ultrasonic irradiation

    e-Polymers

    (2005)
  • Cited by (0)

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