Polymerization solution intercalation

Several techniques such as intercalation of polymer from solution, in-situ intercalative polymerization, melt intercalation, direct mixture of polymer and particulates, template synthesis, in-situ polymerization and solgel process, are being employed for the preparation of polmer-layered silicate nanocomposites. Among them the most common and important approaches are in-situ polymerization, solution-induced intercalation method, and melt processing method, which are briefly discussed below. 

In the melt mixing method, nanoclays are incorporated into the polymer in the molten state. This technique has considerable advantages over either the in situ intercalative polymerization or polymer solution intercalation techniques. Firstly, this method is environmentally benign due to the absence of organic solvents. Secondly, melt processing is compatible with current industrial processes, such as extrusion and injection moulding. The melt intercalation method allows the use of biopolymers that were not suitable for in situ polymerization. This has been the most widely used method in the literature for obtaining PLA/clay nanocomposites. " ... 

Several techniques may be used to produce polymer-MMT nanocomposites, including in-situ polymerization, melt intercalation, and solution casting however, to date in-situ polymerization has produced the best dispersed systems for PS-MMT nanocomposites [8]. This technique offers the advantage of allowing the monomer to penetrate the intergallery spaces first, which aids the exfoliation process. If the polymerization reaction can occur between the clay layers, the delamination process is further enhanced as growing polymer chains can push the clay layers apart, which is the main reason for the superior dispersed systems observed [8]. There are several in-situ polymerization techniques which may be used to form... 

Several methods have been used to obtain polymer nanocomposites by using organoclays [29-32], i.e. solution intercalation [33-39], melt intercalation [40, 41], and in situ interlayer intercalation [30, 42, 43], Among them, in situ interlayer polymerization relies on swelling of... 

A number of methods have frequently been employed in the production of nanocomposite materials. These include solution intercalation, melt intercalation, polymerization, sol-gel, deposition, magnetron sput-tering, laser, ultrasonication, supercritical fluid, etc. In PHA nanocomposite fabrication, solution intercalation and melt intercalation methods are the most widely explored procedures. However, use of in situ intercalative polymerization, supercritical fluids and electrospinning are shown to be promising and emerging techniques. The performance and quality of a nanocomposite depends on how well the nanofillers disperse or blend into the matrix. Therefore, these methods constitute different strategies to improve the composites thermo-mechanical and physico-chemical properties by enhancing efficient interactions between the nanofiller and the polymer matrices. 

Polymer nanocomposites are synthesized by a variety of methods, which include in situ polymerization, solution polymerization, and melt intercalation. The route for nanocomposite synthesis suggested by Toyota researchers was also based on in situ monomer polymerization in the presence of filler. Subsequently, Giannelis and co-workers [28, 29]... 

Polymer/clay nanocomposites exhibit remarkable improvement in material properties relative to unfilled polymers or conventional composites. These improvements can include increased tensile modulus, mechanical strength, and heat resistance and reduced gas permeability and flammability [1], There are various methods of preparing polymer/clay nanocomposites (i) in situ polymerization, (ii) solution intercalation, (iii) melt intercalation, and (iv) in situ template synthesis [2],... 

In summary, fiame retardant polymer-organoclay nanocomposites can be prepared using melt blending, solution blending, or the in situ polymerization method. Intercalated, exfoliated, or intercalated-exfoliated morphology is formed in the polymer matrix. Addition of fiame retardant additives hardly affects nanocomposite formation. Specifically, fiame retardant additives are introduced into the polymer nanocomposite formulation by three approaches ... 

Usually, only intercalated structures with low poly(styrene sulfonate), poly(vinyl sulfonate), poly(acrylic acid), poly(ethylene oxide), and dioctyl sulfosuccinate LDH nanocomposites.Thermoplastic nanocomposites based on LDH are usually prepared by solution intercalation or in situ polymerization. In our previous work we showed that it is also possible to get delamination of LDH in thermoplastic polymers by melt compounding when a suitable inter-or intralayer composition of LDH and proper processing conditions are selected. ... 

Bio-nanocomposites can be prepared by several methods which include in situ polymerization, solution exfoliation, and melt inteicalatioa In the in situ polymerization method, monomers are migrated into the galleries of layered silicates and subsequently polymerized via heat, radiation, or catalyst. In solution exfoliation, layered clays are exfoliated into single platelets. Exfoliation is achieved by dispersing the layered clays in a solvent. The polymer is adsorbed onto the platelets by mixing in the clay suspension. The solvent is removed either by evaporation or by precipitation. In melt intercalation, layered clays are mixed with the polymer matrix in molten state (Zeng et al., 2005). 

To achieve improved dispersibUity of nanoclay fillers within polymer systems, three familiar methods are commonly used, namely, melt intercalation, solution intercalation, and in situ polymerization. The melt-intercalation method is based on the melting point of polymer matrices and is applied by annealing above the melting point of the polymer (Reddy et al., 2013). This method has been chosen by industrial sectors to produce polymer/clay nanocomposites. However, it is not apphcable to the fabrication of biobased polymer/clay nanocomposites based on thermosetting materials such as epoxy and polyester due to their high viscosities (Wypych and Satyanarayana, 2005 Wang et al., 2014). Therefore, the fabrication of biobased thermosetting polymer/clay nanocomposites is mainly based on solution intercalation or in sim polymerization. 

Different paths have been proposed to prepare PC nanocomposites, such as solution intercalation, in situ polymerization and melt intercalation. 

Preparation of nanocomposite polymer can be done by three important methods intercalation of the polymer from a solution, intercalation in the melt state, and in situ polymerization [59]. 

Wang et aL [31] used the solution intercalation of an organoclay to get pecuhar optical properties. In this case, the clay (saponite) was intercalated with a suitable compound bearing chromophore moieties. Ni et at [32] tried to use an amine-functionalized attapulgite as chain extender (instead of a diamine) in the polymerization reaction. The best mechanical performance was achieved by dispersing 2-5 wt% organophilic attapulgite in the polyurethane. 

Traditionally, organoclay-polymer nanocomposites were synthesized by either the solution intercalation method or in-situ intercalative polymerization. However, it was the possibility of direct melt intercalation by... 

From the above discussion, it can be seen that the method adopted to prepare nanocomposites is highly dependent on the nature of the polymer. When the polymers or monomers are water soluble, they can be incorporated into the pristine LDH without any organo-modification due to their good affinity with the LDH. Additionally, the aqueous environment is compatible with the condition for the synthesis of LDH materials. Therefore, water-soluble polymer-LDH nanocomposites can be prepared using some special methods such as in situ synthesis, ion exchange and reconstruction. In the case of water-insoluble polymers and monomers, their nanocomposites are usually prepared in orga-nosolvent (solution intercalation method, exfoliation-absorption method and in situ polymerization method) or molten polymer (melt intercalation method). However, emulsion polymerization and suspension polymerization are methods that allow the incorporation of a water insoluble polymer into an LDH in water. The following sections are devoted to polymer-LDH nanocomposites obtained via emulsion polymerization and suspension polymerization. 

The process of separating the nanoclay platelets is referred to as the intercalation process. Without this separation, the nanoclay would not be capable of allowing the polymer to penetrate the platelet layers. There are two techniques for intercalating the matrix polymer molecule between clay platelets melt intercalation and solution intercalation. In case of melt intercalation, a layered silicate is mixed with the polymer matrix material in the molten state. In case of solution intercalation, the modified nanoclay is swelled in monomer, allowing it to enter the clay gallery. Subsequently, the monomer is polymerized with the result that polymer is formed inside the clay gallery. In either case, once mixed the clay platelet material swells in the polymer matrix and forms a very strong interaction with the polymer chains to produce a composite matrix with enhanced performance. 

Polyimide-clay nanocomposites constitute another example of the synthesis of nanocomposite from polymer solution [70-76]. Polyimide-clay nanocomposite films were produced via polymerization of 4,4 -diaminodiphenyl ether and pyromellitic dianhydride in dimethylacetamide (DMAC) solvent, followed by mixing of the poly(amic acid) solution with organoclay dispersed in DMAC. Synthetic mica and MMT produced primarily exfoliated nanocomposites, while saponite and hectorite led to only monolayer intercalation in the clay galleries [71]. Dramatic improvements in barrier properties, thermal stability, and modulus were observed for these nanocomposites. Polyimide-clay nanocomposites containing only a small fraction of clay exhibited a several-fold reduction in the... 

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