In situ polymerization

In situ polymerization is a method in which inorganic whiskers are evenly dispersed in reactive monomers (or their soluble prepolymers) and then are polymerized using a method identical to bulk polymerization. At the beginning of the reaction, monomers are prepolymerized and then deposited on the surface of whiskers after the prepolymers increasingly aggregate to obtain composite materials filled with whiskers. 

In this way, inorganic whiskers can be uniformly dispersed in a polymer matrix, and the composite material obtained has good processing performance. 

For example, Chen et al. prepared zinc oxide whisker/ polyaniline core-shell composite material using in situ polymerization. The specific operation is as follows. A certain amount of treated zinc oxide whiskers, aniline, and ethanol are well mixed then the appropriate amount of 0.01 mol/L HCl is added dropwise with stirring in an ice bath of 0-2°C to initiate polymerization and the mixture is reacted for 10 minutes. The reaction mixture is centrifuged, filtered, and then dried in a vacuum furnace at 50°C for 24 h. 

3 Performance Analysis of Polymer Matrix Composites Filled with Inorganic Whiskers 

The polymerization of LB materials during deposition (as monolayers either on the subphase surface or on a substrate) is usually experimentally more difficult and time-consuming than either pre- or post-deposition polymerization. There are thus fewer examples in the literature of this mode of polymerization. 

Vinyl stearate (7) was one of the first materials to be investigated for its polymerization behaviour, either on the water surface [23] or in LB multilayers [24]. Polymerization on the water surface yields highly rigid monolayers that are incapable of LB deposition. The monomer deposits X-type, and can be polymerized with UV or y-irradiation by way of a free-radical addition mechanism to produce the polymer (8). This mechanism is common for many such materials, and great care must be taken to avoid quenching of the radical intermediates by impurities, particularly oxygen. It is therefore usually necessary to carry out the polymerization in an inert atmosphere. 

The monolayer polymerization of substituted butadienes (9) is also well known [25]. The aqueous subphase is critical for the materials, since it provides the vehicle for orienting the molecules such that polymerization can take place. The polymerization of other forms of these materials (crystalline, solution or melt) was found to be unsuccessful. 

Substituted diacetylenes (10) comprise a well-studied family of materials, particularly for their polymerization behaviour after deposition in the multilayer state. However, it is also possible to polymerize monomers on the subphase surface prior to deposition [26]. Polymerization has been carried out using ultraviolet (UV) irradiation (254 nm) of energy 50Wm at the subphase surface under a nitrogen ambient. Conversion to 90% polydiacetylene is usually achieved within 

If the diacetylene is solid-state polymerized, dissolved and respread on the subphase, a monolayer is produced with much lower 11 and viscosity than the corresponding surface polymerized material. This illustrates the fact that in some cases polymer properties can be strongly influenced by the polymerization mode, and if specific material parameters are required, it may be an advantage to use one polymerization technique in preference to another. However, in contrast, almost identical U-A behaviour has been reported for structure (10) with n = 12, m = 8 when polymerized on the subphase surface (UV irradiation for 1 h at a surface pressure of 10 mN m under a nitrogen atmosphere), and when prepolymerized in solution (using 2,2 -azoisobutyronitrile in toluene at 60 for 20 h) [27]. This emphasises the difficulty in predicting polymer properties each material system will exhibit characteristic behaviour, depending not solely on the molecular structure, but also on primary factors such as the mode of polymerization and the specific experimental conditions. 

In this method, the nanoparticles are dispersed in monomer followed by polymerization. This method is useful for the preparation of composites with polymers that cannot be processed by solution or melt mixing, for example, insoluble and thermally unstable polymers [168,169]. 

In situ polymerization was the first method used to synthesize polymer-clay nanocomposites based on polyamide (PA) 6. In this technique, the modified layered silicate is swollen by a liquid monomer or a monomer solution. The monomer migrates into the galleries of the layered silicate, so that the polymerization reaction can occur between the intercalated sheets. The reaction can be initiated either by heat or radiation, by the diffusion of a suitable initiator or by an organic initiator or catalyst fixed through cationic exchange inside the interlayer before the swelling step by 

In situ polymerization has been widely used for the preparation of PMMA-CNT composites [180-183]. Conducting polymers are attached to CNT surfaces by in situ polymerization to improve the processability and electrical, magnetic, and optical properties of CNTs [184-187]. PU/MWNT [188,189] and PA/MWNT [190] composites were also synthesized by this method. 

PPy-coated MWNTs by changing the monomer concentration ((a) MWNT PPy = 1 2 (b) MWNTiPPy = 1 5), the layer thickness of polymerized PPy changed, resulting in different electrical properties. Sahoo et al. [191]. Reproduced with permission of Elsevier. 

Compared with other methods, the method of in situ polymerization has the advantage of better compatibility of the systems, and the composites show good dispersion and mechanical properties. 

Zhou et al. [153] investigated the dielectric properties of surface-hydroxylated BaTiOs (h-BaTi03)/PVDF composites. Compared with crude BaTiOs/PVDF composite, the h-BaTi03/PVDF composite showed lower loss tangent, higher dielectric strength, and weaker temperature and frequency dependences. The dielectric properties of the composites were improved due to the strong interaction between h-BaTiOs fillers and PVDF matrix. 

Sonoda et al. [155] observed an increase in relative permittivity of BST/polymer composites by introducing aliphatic carboxylic aids onto the BST surface. The modified nanoparticles with longer carboxylic acid chains had better compatibility with the polymer matrix. In addition, the mechanical properties of modified BST powder/polymer composites were not affected. 

Velasco-Santos et al. (28) also reported the in-situ polymerization of methyl methacrylate with both the treated and untreated nanotubes to generate polymer nanocomposites. The amount of initiator AIBN, reaction time and temperature were controlled to tune the molecular weight of polymer in the composites. The treated nanotubes had COOH and COO- functionalities on the sidewalls 

The polymerization of a monomer in a polymer matrix is known to be a versatile and practical method for the in situ preparation of new materials [24]. This method yields a more intimate mixing of two components. 

Polypyrrole has been deposited on the surface of microporous PE films by gas-phase oxidative polymerization [25-28]. In this approach, microporous PE films were treated with a 1 M solution of ferrous chloride in methanol and then exposed to pyrrole vapours in a reaction vessel. The films were removed after a certain time interval, washed with either methanol or ethanol and dried. The deposited polypyrrole was further protonated (doped) by treatment with hydrochloric acid [25, 27]. Tishchenko et al. (2002) obtained a 48 wt. % deposition of polypyrrole after 144 hours of polymerization [27]. 

Sulphonated PE films (PE films grafted with polystyrene sulphonlc acid) have also been coated through in situ polymerization of polypyrrole [33-37]. The films were placed in a vessel and the required volimies of pyrrole and iron (111) chloride solution to submerge the films were introduced simultaneously into the vessel. As the polymerization progressed, the films darkened and a black precipitate also formed in the reaction mixture. Similarly, Elyshevich et al. (2006) prepared electroactive composites through oxidative polymerization of pyrrole on porous PE films [38], 

In situ oxidative polymerization has also been used to prepare polyaniline/ PE composites. In one approach, microporous PE films were immersed in a solution of aniline hydrochloride and polymerization was started by the introduction of ammonium peroxydisulfate [27, 39], Similarly, Wan and Yang (1993) obtained polyaniline/ PE composites using 

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-situ polymerization consists of three steps. In the first step, the clay is converted to organophilic. In this process, the preparation of the organically modified clay is synthesized from the normally available hydrophilic clay mineral and the surface is modified using surfactants. The second step consists of intercalation of the monomer, assisted by the presence of surfactant, which is followed by the polymerization of the monomer to prepare long-chain nanoclay. In other words, in this process a polymer precursor or a monomer is subjected to get embedded in between clay layers followed by the expression of the silicate platelet layers into the clay matrix undergoing polymerization. 

Sodium montmorillonite (Na-MMT) was originally modified with pro-tonated amino acids with different numbers of carbon atoms and subsequently swollen with e-caprolactam. Then it underwent polymerization to produce nylon-6 polymer-clay nanocomposite [18]. Later, this technique was also extended to manufacture other thermoplactics. One advantage of this in-situ polymerization technique is the tethering effect, which enables the organic chemical such as 12-aminododecanoic acid (ADA) situated at the surface of the nanoclays to link with nylon-6 polymer chains during polymerization. 

Another technique that has been used to make PMMA nanocomposites is in situ polymerization since the 1960s (Blumstein, 1965 Huang and Brittain, 2001 Lee and Jang, 1996). It is a method involving dispersing nanoparticles in a monomer 

Wang et al. (2002) compared various in situ polymerization methods for the preparation of PMMA/clay nanocomposites. It was found that the particular preparative technique that is used has a large effect on the type of nanocomposites (in terms of nanoclay dispersion) that may be obtained. Solution polymerization of MMA only yields intercalated nanocomposites regardless of the presence of polymerizable double bond in the intergallery region. On the other hand, emulsion, suspension, and bulk polymerization can yield either exfoliated (with intergallery double bond) or intercalated (without double bond present) nanocomposites. 

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Decabromodiphenyl Oxide—Polyacrylate Finishes. An alternative to the diffusion technique is the appHcation of decabromodiphenyl oxide on the surface of fabrics in conjunction with binders (131). Experimental finishes using graft polymerization, in situ polymerization of phosphoms-containing vinyl monomers, or surface halogenation of the fibers also have been reported (129,130,132,133). 

There are several approaches to the preparation of multicomponent materials, and the method utilized depends largely on the nature of the conductor used. In the case of polyacetylene blends, in situ polymerization of acetylene into a polymeric matrix has been a successful technique. A film of the matrix polymer is initially swelled in a solution of a typical Ziegler-Natta type initiator and, after washing, the impregnated swollen matrix is exposed to acetylene gas. Polymerization occurs as acetylene diffuses into the membrane. The composite material is then oxidatively doped to form a conductor. Low density polyethylene (136,137) and polybutadiene (138) have both been used in this manner. 

Bis-maleimide resins composed of BMI and diamines have been reported in the early 1960s in the patent literature. Since that time, a number of patents have appeared describing improvements in their properties and uses [3]. Although many bis-maleimide resins are commercially developed, relatively few reports of their use as adhesives are to be found in scientific journals [4-10]. Improvements of maleimide resins are mirrored in the improvements of thermosetting polyimides. For example, the method of in situ polymerization of monomer reactants (PMR method) was developed [6]. 

Continuous porous polymer rods have been prepared by an in situ polymerization within the confines of a chromatographic column. The column is filled with glycidyl methacrylate and ethylene dimethacrylate monomer mixtures, cyclo-hexanol and dodecanol diluents, and AIBN initiator. They are then purged with nitrogen, stopped, and closed with a silicon rubber septum. The polymerization is allowed to proceed for 6 hr at 70°C with the column acting as a mold (47). 

Recently, an in-depth review on molecular imprinted membranes has been published by Piletsky et al. [4]. Four preparation strategies for MIP membranes can be distinguished (i) in-situ polymerization by bulk crosslinking (ii) preparation by dry phase inversion with a casting/solvent evaporation process [45-51] (iii) preparation by wet phase inversion with a casting/immersion precipitation [52-54] and (iv) surface imprinting. 

SCHEME 2.3 The in situ polymerization method for nanocomposite preparation. 

This mbber is very tacky in nature and contains acrylic group, which makes it polar in nature. Nanocomposites have been prepared based on this elastomer with a wide range of nanohllers. Layered silicates [53-55] have been used for this preparation. Sol-gel method [56,57], in situ polymerization [58], and nanocomposites based on different clays like bentonite [59] and mica [60] have been described. The mechanical, rheological, and morphological behaviors have been investigated thoroughly. 

The first nanocomposite prepared by Toyota Group of Japan was based on nylon 6. In situ polymerization of caprolactum inside the gallery of 5% MMT resulted in the first nylon 6-clay nanocomposite. Besides nylon, polypropylene (PP) is probably the most thoroughly investigated system. Excepting the study of the various properties, theoretical aspects and simulations have also... 

This is a highly polar polymer and crystalline due to the presence of amide linkages. To achieve effective intercalation and exfoliation, the nanoclay has to be modified with some functional polar group. Most commonly, amino acid treatment is done for the nanoclays. Nanocomposites have been prepared using in situ polymerization [85] and melt-intercalation methods [113-117]. Crystallization behavior [118-122], mechanical [123,124], thermal, and barrier properties, and kinetic study [125,126] have been carried out. Nylon-based nanocomposites are now being produced commercially. 

In Situ Polymerization and the Sol-Gel Reaction OE Organic-Inorganic Components... 

There are three general approaches to the synthesis of polymer-clay nanocomposites. In the first approach, a monomer or precursor is mixed with organophilic clay and followed by polymerization. This in situ polymerization technique was first developed by the... 

Nylon-6-clay nanocomposites were also prepared by melt intercalation process [49]. Mechanical and thermal testing revealed that the properties of Nylon-6-clay nanocomposites are superior to Nylon. The tensile strength, flexural strength, and notched Izod impact strength are similar for both melt intercalation and in sim polymerization methods. However, the heat distortion temperature is low (112°C) for melt intercalated Nylon-6-nanocomposite, compared to 152°C for nanocomposite prepared via in situ polymerization [33]. 

Poly(acrylic acid) and its salts have been known to have useful binding properties for some thirty years they have been used for soil consolidation (Lambe Michaels, 1954 Hopkins, 1955 Wilson Crisp, 1977) and as a flocculant (Woodberry, 1961). The most interesting of these applications is the in situ polymerization of calcium acrylate added to soil (de Mello, Hauser Lambe, 1953). But here we are concerned with cements formed from these polyacids. 

Chemicals for Water Shutoff In Situ Polymerization, Polyaddition, and Condensation... 

Recently, many synthetic polymers such as urea/formalin resin, melamine/formalin resin, polyester, and polyurethane have been widely used as the wall material for the microcapsule, though the gelatin microcapsule is still used. Microcapsules using a synthetic polymer wall have several advantages over those using a gelatin wall (1) the preparation process is simple, (2) the size of the microcapsules is well balanced, (3) the microcapsule concentration can be increased twofold or more and (4) the microcapsules have a high resistance to water and many chemicals. Synthetic microcapsules are prepared by interfacial polymerization or in situ polymerization. 

Taviot-Gueho C, Leroux F (2005) In situ Polymerization and Intercalation of Polymers in Layered Double Hydroxides 119 121-159 Teitel baum GB, see Kochelaev BI (2005) 114 205-266 Thessing J, see Peng X (2005) 118 137-177 Trommer K, see Roewer G (2002) 101 59-136 TsuzukiS (2005) Interactions with Aromatic Rings 115 149-193... 

The in situ bulk polymerization of vinyl monomers in PET and the graft polymerization of vinyl monomers to PET are potential useful tools for the chemical modification of this polymer. The distinction between in situ polymerization and graft polymerization is a relatively minor one, and from a practical point of view may be of no significance. In graft polymerization, the newly formed polymer is covalently bonded to a site on the host polymer (PET), while the in situ bulk polymerization of a vinyl monomer results in a polymer that is physically entraped in the PET. The vinyl polymerization in the PET is usually carried out in the presence of the swelling solvent, thereby maintaining the swollen PET structure during polymerization. The swollen structure allows the monomer to diffuse in sufficient quantities to react at the active centers that have been produced by chemical initiation (with AIBM) before termination takes place. 

Williams, E.G., Contaminant containment by in situ polymerization, in Proc. Second National Symposium on Aquifer Restoration and Ground Water Monitoring, National Water Well Association, Worthington, OH, 1982. 

Polymeric conducting systems were also prepared by in situ polymerization of vinyl monomers in ionic liquids [22], with a conductivity of 1 mS/cm. A conductive polymer electrolytes were also prepared by polymerization in liquid EMIm(HF)nF leading to a composite poly(2-hydroxyethyl methacrylate)-EMIm(HF)nF. Recently, polymer electrolytes were prepared in the form of thin foils, by incorporating ionic liquids in a polymer matrix [13-15], Conductivities of polymer-IL or polymer-IL-solvent systems are collected in Table 4. 

Porous polymer materials, especially in particulate form, are of interest in a diverse range of applications, including controlled drug delivery, enzyme immobilization, molecular separation technology, and as hosts for chemical synthesis [101-104]. MS materials have been used as hosts for the template synthesis of nanoporous polymer replicas through in situ polymerization of monomers in the mesopores [105-108]. 

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