Terminal-functionalized polymers

The distinctive properties of densely tethered chains were first noted by Alexander [7] in 1977. His theoretical analysis concerned the end-adsorption of terminally functionalized polymers on a flat surface. Further elaboration by de Gennes [8] and by Cantor [9] stressed the utility of tethered chains to the description of self-assembled block copolymers. The next important step was taken by Daoud and Cotton [10] in 1982 in a model for star polymers. This model generalizes the... 

Terminal-functionalized polymers such as macromonomers and telechelics are very important as prepolymer for construction of functional materials. Single-step functionalization of polymer terminal was achieved via lipase catalysis. Alcohols could initiate the ring-opening polymerizahon of lactones by lipase catalyst. The lipase CA-catalyzed polymerizahon of DDL in the presence of 2-hydroxyethyl methacrylate gave the methacryl-type polyester macromonomer, in which 2-hydroxyethyl methacrylate acted as initiator to introduce the methacryloyl group quanhtatively at the polymer terminal ( inihator method ).This methodology was expanded to the synthesis of oo-alkenyl- and alkynyl-type macromonomers by using 5-hexen-l-ol and 5-hexyn-l-ol as initiator, respechvely. 

Structural control of polymer terminal has been extensively studied since terminal-functionalized polymers, typically macromonomers and telechelics, are often used as prepolymers for synthesis of functional polymers. Various methodologies for synthesis of these polymers have been developed however, most of them required elaborate and time-consuming procedures. By selecting... 

The first example of Iiving polyolefin with a uniform chain length was found in the low-temperature polymerization of propylene with the soluble catalyst composed of V(acac)3 and Al(C1Hi)2Cl. The mechanism of the living coordination polymerization is discussed on the basis of the kinetic and stereochemical data. Subsequently, some applications of living polypropylene are introduced to prepare tailor-made polymers such as terminally functionalized polymers and block copolymers which exhibit new characteristic properties. Finally, new types of soluble Ziegler-Natta catalysts are briefly surveyed in connection with the synthesis of living polyolefins. 

Macromolecular metal complexes of dendrimers have a number of properties, which make them promising for use in catalysis. Firstly, they are relatively readily separable from the reaction products by precipitation with a poor solvent or by membrane filtration. Secondly, the introduction of catalytically active sites into dendrimers is controllable in this they resemble terminally functionalized polymers. The dendrimer structure allows us to purposefully introduce catalytically active groups into the dendrimer core, onto the outer surface, or in intermediate positions. The introduction of cataljdically active groups to the outer surface makes them accessible to reaction and enables us to obtain a catalyst that has a high metal content owing to the dendrimer structure. The introduction of catalytically active... 

Using terminally functionalized polymers such as asymmetric PEG molecules, furthermore biomimetic devices can be created. For example, amine reactive N-succinimidyl tartrate monoamine poly(ethylene glycol)-block-poly(D,L-lactic acid) (ST-NH-PEGxPLAy) as well as thiol-reactive polymers using 3-maleinimido propionate as a linker (see Figure 12) can be prepared in order to create biomimetic surfaces upon reaction with proteins or small adhesion peptides. 

Functionalized initiators. Their use leads to terminal functionalized polymers. Thus, with phosphorus-containing ketene silyl acetals, trimethylsilyl methyl sulfide, trimethylsilyl cyanide, dimethylketene-bis(trimethylsilyl)acetal, or dimethylketene-2-(trimethylsiloxy) ethyltrimethyl silyl acetal, terminal phosphoric acid groups, thiomethyl groups, and cyanide, hydroxy, or carboxyl groups are readily introduced [234]. Furthermore, the styrene end group can also be achieved [247]. 

The ability to produce polymers of well-defined structure using anionic polymerization is of great importance and despite the above difficulties it is widely used for this purpose. Thus polymers with narrow molar mass distributions, terminally-functionalized polymers, and perhaps most important of all, well-defined block copolymers (Section 2.16.9) can be prepared using anionic polymerization. 

Several different transformations have been used, e.g. anionic to cationic, cationic to anionic, and anionic to free-radical polymerization. An up-to-date review should be consulted for details of these and other methods (e.g. coupling of terminally-functionalized polymers) of block copolymer preparation. 

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