Functionalized polymers with synthesis

These results illustrate the diversity of synthetic and processing approaches that can be taken in the synthesis of thin-film frequency doubling materials. Specifically, we have demonstrated that it is possible to assemble chromophore-functionalized polymers with greater than one chromophore substitutent per monomer subunit, with d33 values as high as 65 x 10 esu, with Tg values as high as 173°C, with improved temporal stability, and with good transparency characteristics at A 0.633 fim. We have also shown that known chromophore-functionalized polymers can be simultaneously poled and cross-linked... 

A class of end-functionalized polymers with polymerizable terminal groups are generally called macromonomers. By both functional initiator and terminator methods, a variety of macromonomers have been synthesized in living cationic polymerization of vinyl ethers, styrenes, and isobutene, as summarized in Table 3 [16,31,147,149-151,155,158-171]. Some of these macromonomers are used in the synthesis of graft polymers (Section VI.C). 

Gao, H. Matyjaszewski, K. Synthesis of functional polymers with controlled architecture by GRP of monomers in the presence of cross-linkers From stars to gels. Prog. Polym. Sci. 2009, 34 (4), 317-350. 

The synthesis and dilnte and hulk solution properties of end-functionalized polymers with zwitterionic end groups have recently been reviewed (187). Reportedly, such polymers with different architectures (linear, block, and star copolymers) can be prepared by means of anionic polymerization. First, dimethylamine groups were introduced by using 3-dimethylaminopropyllithium as functional initiator. This group was then switched to sulfozwitterionic one by reaction with propanesultone. 

Although the structure/property relationships have become more evident for alkyl substituted polythiophenes, the synthesis and characterization of new heterofunctionalized polythiophenes continues to be an active research area because there are a number of potential applications for new materials. There is still much to be learned about the structure/property relationships in these functionalized polymers. The effects of these side chains on the stability, solubility and self-assembly of these polymers as well as their effects on the electronic, optical and electrooptical properties are largely unknown. An improved understanding of the structure/property relationships will, in turn, drive the rational synthesis of new, functionalized polymers with optimized properties. 

Synthetic strategies for the preparation of polymer brushes (A) physisorption, (B) grafting-to approach via reaction of appropriately end-functionalized polymers with complementary functional groups on the substrate surface, (C) grafting-from approach via surface-initiated polymerization. (Reprinted with permission from Barbey et al. 2009. Polymer Brushes via Surface-Initiated Controlled Radical Polymerization Synthesis, Characterization, Properties, and Applications. Chemical Reviews 109 (ll) 5437-5527 copyright (2009) American Chemical Society.)... 

The methodology of living anionic polymerization, especially alkyllithium-in-itiated polymerizations of styrene and diene monomers, is particularly suitable for the synthesis of functionalized polymers with well-defined structures [3, 137]. Since these living polymerizations generate stable, anionic polymer chain ends (PLi) when all of the monomer has been consumed, post-polymerization reactions with a variety of electrophilic species (X-Y) can be used to generate polymers with a diverse array of functional end groups (P-X) as illustrated in Eq. (29) [8] ... 

Higashihara, T, Hayashi, M., and Hirao, A. (2002) Synthesis of branched polymers by means of Uving anionic polymerization, 9 Radical coupling reaction of 1,1-diphenylethylene-functionalized polymers with potassium naphthalenide and its application to syntheses of in-chain-functionalized polymers and star-branched polymers. Macromolecular Chemistry and Physics, 203,166-175. 

Sonochemistry is also proving to have important applications with polymeric materials. Substantial work has been accomplished in the sonochemical initiation of polymerisation and in the modification of polymers after synthesis (3,5). The use of sonolysis to create radicals which function as radical initiators has been well explored. Similarly the use of sonochemicaHy prepared radicals and other reactive species to modify the surface properties of polymers is being developed, particularly by G. Price. Other effects of ultrasound on long chain polymers tend to be mechanical cleavage, which produces relatively uniform size distributions of shorter chain lengths. 

End-functional polymers, including telechelic and other di-end functional polymers, can be produced by conventional radical polymerization with the aid of functional initiators (Section 7,5.1), chain transfer agents (Section 7.5.2), monomers (Section 7.5.4) or inhibitors (Section 7.5.5). Recent advances in our understanding of radical polymerization offer greater control of these reactions and hence of the polymer functionality. Reviews on the synthesis of end-functional polymers include those by Colombani,188 Tezuka,1 9 Ebdon,190 Boutevin,191 Heitz,180 Nguyen and Marechal,192 Brosse et al.rm and French.194... 

Depending on the choice of transfer agent, mono- or di-cnd-functional polymers may be produced. Addition-fragmentation transfer agents such as functional allyl sulfides (Scheme 7.16), benzyl ethers and macromonomers have application in this context (Section 6.2.3).212 216 The synthesis of PEG-block copolymers by making use of PEO functional allyl peroxides (and other transfer agents has been described by Businelli et al. Boutevin et al. have described the telomerization of unsaturated alcohols with mercaptoethanol or dithiols to produce telechelic diols in high yield. 

Ebdon and coworkers22 "232 have reported telechelic synthesis by a process that involves copolymerizing butadiene or acetylene derivatives to form polymers with internal unsaturation. Ozonolysis of these polymers yields di-end functional polymers. The a,o>dicarboxy1ic acid telechelic was prepared from poly(S-s tot-B) (Scheme 7.19). Precautions were necessary to stop degradation of the PS chains during ozonolysis. 28 The presence of pendant carboxylic acid groups, formed by ozonolysis of 1,2-diene units, was not reported. 

There are additional factors that may reduce functionality which are specific to the various polymerization processes and the particular chemistries used for end group transformation. These are mentioned in the following sections. This section also details methods for removing dormant chain ends from polymers formed by NMP, ATRP and RAFT. This is sometimes necessary since the dormant chain-end often constitutes a weak link that can lead to impaired thermal or photochemical stability (Sections 8.2.1 and 8.2.2). Block copolymers, which may be considered as a form of end-functional polymer, and the use of end-functional polymers in the synthesis of block copolymers are considered in Section 9.8. The use of end functional polymers in forming star and graft polymers is dealt with in Sections 9.9.2 and 9.10.3 respectively. 

The synthesis of end functional polymers by NMP, ATRP and RAFT has already been discussed in Section 9.7. The "grafting to approach involves the covalent attachment of an end-funetionalized polymer with reactive surface groups on the substrate. The approach is inherently limited by the crowding of chains at the surface and the limit this places on the final graft density. 

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