Comparison with conventional polymers

Vegetable oil-based hyperbranched polymers are prepared mainly by double monomer methodology (DMM), although single monomer methodology (SMM) may also be used. 

In SMM methodology, AB or latent AB , monomers are polymerised to obtain hyperbranched polymers. In general, in accordance with the reaction mechanism, there are two different routes (i) poly-condensation of AB , monomers and (ii) self-condensation vinyl polymerisation (SCVP). However, this methodology is not popular in the preparation of vegetable oil-based polymers, but as these approaches are significant in obtaining highly branched polymer and can also be used for this purpose, they are briefly described here. 

In this approach, AB2 type or other similar monomers such as AB (x = 4, 6, 8, etc.) monomers are polymerised by a polycondensation reaction. Gelation, a general problem in the polymerisation of multifunctional monomers, is avoided by the use of a dilute solution and the slow addition of monomer(s). Vegetable oil-based hyperbranched polyhydrocarbons, polyethers, polyesters, polyamides, and so on may be prepared by this method. 

The double monomer methodology (DMM) is also used to obtain vegetable oil-based hyperbranched polymers. In this approach, direct polymerisation of two types of monomers or monomer pairs generates hyperbranched polymers. DMM can be divided into two main subclasses based on the selected monomer pairs and reaction pathways. In this technique, an A2 with a Bj monomer causes polymerisation, known as an A2 + B3 approach, or a monomer pair generates an in situ AB intermediate to form hyperbranched polymer. The last approach is known as couple monomer methodology (CMM). 

The most important factor in this approach for obtaining a hyperbranched polymer is the choice of a suitable monomer pair (AA and BB 2). This follows the same conditions as above if the reactivity of A is identical to A and B is equal to B. Cross-linking will be minimised if an asymmetric monomer AA or BB% is used.  

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Typically IPNs exhibit some degree of phase separation in their structure depending on how miscible the component polymers are. However, because the networks are interconnected such phase separation can occur only to a limited extent, particularly by comparison with conventional polymer blends. Polymer blends necessarily have to be prepared from thermoplastics IPNs may include thermosets in their formulation. 

As a resume the rheological responses of MCLCP solutions (in comparison with conventional polymer solutions) to the most important variables are shown (qualitatively) in the comprehensive Fig. 16.36. 

Table 9-8. Dielectric Properties of Plasma-Polymerized Films in Comparison with Conventional Polymers at Temperature 20°C and Frequency 1 kHz...

Properties of Polymer Cement in Comparison with Conventional Cement... 

Because observed rate enhancements are usually small, or zero, nonthermal effects do not seem to be important in MW heated reactions in homogeneous media, except possibly in some reactions of polymers and reactions in nonpolar solvents. Relatively few studies have been conducted on MW-assisted reactions of polar reactants in nonpolar solvents. Also, since there is some disagreement as to whether or not these reactions are accelerated significantly by MW, in comparison with conventionally heated reactions at the same temperature, more research on the effect of MW irradiation on the rates of these reactions is required. Nonthermal effects may, however, explain the more substantial MW rate enhancements in solvent-free reactions on solid supports [44] (see Chapt. 5) and solid state reactions [68, 69]. 

Abstract Recent developments in the microwave-assisted synthesis of heterocycles are surveyed with the focus on diversity-oriented multi-component and multi-step one-pot procedures. Both solution- and solid-phase as well as polymer-supported methodologies for the preparation of libraries of heterocycles are reviewed. Advantages of microwave dielectric heating are highlighted by comparison with conventional thermal conditions. 

Mechanochemical processing has been used to conduct the esterification of poly(vinyl alcohol) (PVA) with maleic anhydride through stress-induced reaction by pan-milling (Scheme 8.5). In comparison with conventional methods for the esterification of PVA, this protocol is viable and environmentally friendly and can be an effective technique for the chemical modification of polymers. ... 

Abstract This chapter describes vegetable oil-based polymer nanocomposites. It deals with the importance, comparison with conventional composites, classification, materials and methods, characterisation, properties and applications of vegetable oil-based polymer nanocomposites. The chapter also includes a short review of polymer nanocomposites of polyester, polyurethanes and epoxies based on different vegetable oils and nanomaterials. The chapter shows that the formation of suitable vegetable oil-based polymer nanocomposite can be considered to be a means of enhancing many of the desirable properties of such polymers or of obtaining materials with an intrinsically new set of properties which will extend their utility in a variety of advanced applications. Vegetable oil-based shape memory hyperbranched polyurethane nanocomposites can be sited as an exampie of such advanced products. 

Wu et al. reported that surfactant-free stable polystyrene nanoparticles could be prepared by applying microwave irradiation with KPS as an initiator in water solutions [41]. In comparison with conventional heating, this method can shorten the reaction time by a factor of 20, results in narrowly distributed nanoparticles, and leads to moderately distributed polymer chains inside the nanoparticles (Table 3). The reactions were conducted in a multimode microwave cavity with maximum output of 900 W, wherein a reaction flask equipped with a stirrer and reflux condenser and charged with 250 ml of the reaction mixture was irradiated. Typically, under reduced microwave irradiation power (SOW), the reaction temperature was maintained at 70 °C, which led to 98% conversion of styrene within 40 min [42]. 

There have been attempts to use metal oxide-CB composites for gas sensor design (Liou and Lin 2007). However, such an approach does not give any improvement in operating characteristics in comparison with conventional metal oxide or CB-polymer-based gas sensors. 

Although the electrochromism of polymer films contains problems in its relatively slow response and higher electricity consumption due to the redox or doping-undoping reactions in comparison with conventional liquid crystal devices, the rich variations of the coatings, the multi-coloured displays, and the easy construction of large-area devices with polymer films should lead to interesting applications. 

N. Pearnchob, and R. Bodmeier, Dry polymer powder coating and comparison with conventional liquid-based coatings for Eudragit RS, ethylcellulose and shellac, Eur. J. Pharm. Biopharm., 56 (3), 363-369, 2003. 

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