Functional end groups

Fig. 2. Functional end groups and solution viscosity during polyester resin manufacture. Acid value is defined as the milligrams of KOH required to neutralize 1 g of polymer hydroxyl value is defined as the milligrams of acid equivalent required to neutralize 1 g of polymer. Solution viscosities are...

General structure of the (Si—X) terminated siloxane oligomers and a list of important reactive functional end groups (X) are given in Table 2. 

Table 2. General structure of (Si—X) terminated organosiloxane oligomers and important functional end groups...

During the synthesis of functional disiloxanes via hydrosilation, the starting materials are usually either tetramethyldisiloxane or dimethylchlorosilane and a proper olefinic (mostly allyl type) compound having the desired functional end group. If dimethylchlorosilane is employed, the hydrosilation is usually followed by hydrolysis. As a specific example, the synt hesis of 1,3-bis(3-glycidoxypropyl)tetramethyldisiloxane is shown in Reaction Scheme IV. 

Ogata, S., Mitsuya, Y, Zhang, H. D., and Fukuzawa, K., "Molecular Dynamics Simulation for Analysis of Surface Morphology of Lubricant Films with Functional End Groups, IEEE Trans. Magn., Vol. 41,2005, pp. 3013-3015. 

Many years have passed since the early days of AFM, when adhesion was seen as a hindrance, and it is now regarded as a useful parameter for identification of material as well as a key to understanding many important processes in biological function. In this area, the ability of AFM to map spatial variations of adhesion has not yet been fully exploited but in future could prove to be particularly useful. At present, the chemical nature and interaction area of the AFM probe are still rarely characterized to a desirable level. This may be improved dramatically by the use of nanotubes, carbon or otherwise, with functionalized end groups. However, reliance on other measurement techniques, such as transmission electron microscopy and field ion microscopy, will probably be essential in order to fully evaluate the tip-sample systems under investigation. 

A thick is deposited on top. This is then covered with a molecularly thin film of lubricant to minimize wear during start-stop contacts and to passivate the disc surface against contamination and corrosion. High-molecular-weight perfluoropolyalkylether (PFPE) polymers are widely used for this purpose. In order to improve surface bonding, the PFPEs are modified with specific functional end groups. All these molecules have similar backbone structures, namely ... 

Living polymerization processes leading to linear copolymeric precursors, with either identical or complementary functional end groups (X,Y) have... 

Detailed studies about metal deposition from the gas phase onto SAMs have been published [108-110], The central question for the system substrate/SAM/deposit there (as well as in electrochemistry) is the exact location of the deposited metal On top of the SAM or underneath Three clearly different situations are easily foreseen (Fig. 31). (1) Metal on top of the SAM. Depending on a strong or weak chemical interaction between metal and SAM (e.g., functional end group of the SAM), the deposit will spread out on top of the SAM or it will cluster on the SAM. (2) Metal penetrating the SAM (e.g., at defects in the SAM) and connecting to the metal substrate underneath the SAM. This configuration is often pictured as a mushroom, with a thin connective neck and a large, bulky head. (3) Deposited metal is inserted be-... 

Reactive impact modifiers are preferred for toughening of PET since these form a stable dispersed phase by grafting to the PET matrix. Non-reactive elastomers can be dispersed into PET by intensive compounding but may coalesce downstream in the compounder. Reactive impact modifiers have functionalized end groups. Functionalization serves two purposes - first, to bond the impact modifier to the polymer matrix, and secondly to modify the interfacial energy between the polymer matrix and the impact modifier for enhanced dispersion. Some examples of commercially available reactive impact modifiers for PET are shown in Table 14.3. An example of a non-reactive elastomer that can be used in combination with reactive impact modifiers is ethylene methyl acrylate (EMA), such as the Optema EMA range of ethylene methyl acrylates manufactured by the Exxon-Mobil Chemical Company (see Section 4.2). 

The alkyllithium-initiated, anionic polymerization of vinyl and diene monomers can often be performed without the incursion of spontaneous termination or chain transfer reactions (1). The non-terminating nature of these reactions has provided methods for the synthesis of polymers with predictable molecular weights and narrow molecular weight distributions (2). In addition, these polymerizations generate polymer chains with stable, carbanionic chain ends which, in principle, can be converted into a diverse array of functional end groups using the rich and varied chemistry of organolithium compounds (3). 

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