Polymerization, inclusion reactions

Cyanoacrylate adhesives cure by anionic polymerization. This reaction is catalyzed by weak bases (such as water), so the adhesives are generally stabilized by the inclusion of a weak acid in the formulation. While adhesion of cyanoacrylates to bare metals and many polymers is excellent, bonding to polyolefins requires a surface modifying primer. Solutions of chlorinated polyolefin oligomers, fran-sition metal complexes, and organic bases such as tertiary amines can greatly enhance cyanoacrylate adhesion to these surfaces [72]. The solvent is a critical component of these primers, as solvent swelling of the surface facilitates inter-... 

Channel Inclusion Compounds, p. 223 Hydrogen Bonding, p. 658 Inclusion Reactions and Polymerization, p. 705 Isostructurality of Inclusion Compounds, p. 767 Organic Zeolites, p. 996 Polymorphism, p. 1129... 

Cyclophanes Definition and Scope, p. 414 Inclusion Reactions and Polymerization, p. 705 Macrocycle Synthesis, p. 830 Naked Anion effect, p. 939... 

Inclusion Reactions and Polymerization, p. 705 Preorganization and Complementarity, p. 1158 Secondary Bonding, p. 1215 Soft and Smart Materials, p. 1302 Solid-State Reactivity/Topochemistry, p. 1316 Strong Hydrogen Bonds, p. 1379... 

Carcerands and Hemicarcerands, p. 189 Crystal Growth Mechanisms, p. 364 DNA Nanotechnology, p. 475 Inclusion Reactions and Polymerization, p. 705 Micelles and Vesicles, p. 861... 

The free radical mechanism is demonstrated by using the polymerization of tetrafluoroethylene to facilitate its understanding. Replacement of the tetrafluoroethylene with the appropriate monomer and inclusion of the specific initiator can illustrate other polymerization reactions that proceed by free radical mechanisms. The reaction is initiated by a catalyst or by an initiator, usually based on the reaction temperature. A bisulfite or persulfate is the typical initiator for higher temperature TFE polymerization. The reaction scheme for persulfate initiation is shown below. 

Our interest from the outset has been in the possibility of crosslinking which accompanies inclusion of multifunctional monomers in a polymerizing system. Note that this does not occur when the groups enclosed in boxes in Table 5.6 react however, any reaction beyond this for the terminal A groups will result in a cascade of branches being formed. Therefore a critical (subscript c) value for the branching coefficient occurs at... 

DNA polymerases normally use 3 -deoxynucleotide triphosphates as substrates for polymerization. Given an adequate concentration of substrate, DNA polymerase synthesizes a long strand of new DNA complementary to the substrate. The use of this reaction for sequencing DNA depends on the inclusion of a single 2/3 -dideoxynucleoside triphosphate (ddNTP) in each of four polymerization reactions. The dideoxynucleotides ate incorporated normally in the chain in response to a complementary residue in the template. Because no 3 -OH is available for further extension, polymerization is... 

Strictly speaking, dihydrofuran compounds do not belong to the field covered by this review. However, their behaviour in polymerization reactions is both similar and cleaner than that of their furanic counterparts and it is felt that their brief inclusion here makes the panorama more complete and perhaps clearer in some respects. 

The process proceeds through the reaction of pairs of functional groups which combine to yield the urethane interunit linkage. From the standpoint of both the mechanism and the structure type produced, inclusion of this example with the condensation class clearly is desirable. Later in this chapter other examples will be cited of polymers formed by processes which must be regarded as addition polymerizations, but which possess within the polymer chain recurrent functional groups susceptible to hydrolysis. This situation arises most frequently where a cyclic compound consisting of one or more structural units may be converted to a polymer which is nominally identical with one obtained by intermolecular condensation of a bifunctional monomer e.g., lactide may be converted to a linear polymer... 

Main group organometallic polymerization catalysts, particularly of groups 1 and 2, generally operate via anionic mechanisms, but the similarities with truly coordinative initiators justify their inclusion here. Both anionic and coordinative polymerization mechanisms are believed to involve enolate active sites, (Scheme 6), with the propagation step akin to a 1,4-Michael addition reaction. 

Photopolymer technology, which encompasses the action of light to form polymers and light initiated reactions in polymeric materials, is an immense topic. Previous papers in this symposium have described some of basic chemistry utilized in photopolymer technology. The primary objectives of this paper are a) to develop the connections between basic photopolymer chemistry and practical uses of the technology and b) to provide an overview of the wide variety of photopolymer applications that have been developed since the 1950 s. Every attempt has been made to make this review as inclusive as possible, but because of the extensive nature of this topic, there are many applications of photopolymer chemistry that have not been included. In addition, only limited representative references are provided since the patent and open literature for this technology are quite vast (7). 

In the second dual photo/thermal initiation strategy, the approach described above is augmented by the inclusion of a thermal initiator. Upon illumination, active centers produced by fragmentation of the photoinitiator start the polymerization reaction. The heat evolved from the exothermic photopolymerization elevates the temperature of the system and results in the production of additional active sites by the thermal initiator. This dual initiating strategy provides both the cure on demand (temporal control) afforded by photopolymerization, and the completeness of cure provided by the thermal initiator. 

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