Post Polymerization Modification

Because of the (partially) living character of the Nd-catalyzed diene polymerization the incorporation of functional end groups is also achieved by post-polymerization reactions. By the incorporation of specific functionalities carbon black or silica fillers are bound better to the rubber. As a consequence vulcanizate properties (tensile strength, rebound and resistance to wear) are improved. 

Branching by bifunctional sulfur derivatives such as SCI2, S2CI2, S0C12 and S2Br2 is claimed by Bayer [427,428]. Especially Nd-BR technology is useful for this post-polymerization modification as it allows for the required low 

Reference without Mooney jump with PCI3 Mooney jump 

In the above-mentioned patents post-polymerization modification is performed in a single step. An alternative is the performance of two sequential modification steps. In the first step the polymer is reacted with tin or germanium derivatives (triphenyl tin, tributyl tin, diphenyl tin dichloride, dioctyl tin dichloride, phenyl tin trichlorde etc.). In the subsequent modification step heterocumulene compounds (ketenes, thioketenes, isocyanates, thioiso-cyanates and carbodiimides) are applied [437,438]. Specific interaction with silica is obtained by end group functionalization with vinyl monomers which contain hydroxyl or epoxy groups. The effects are observed if the PDI is below 5 [439,440]. 

Cyclization can be also achieved in a separate reaction step after polymerization. Cyclization of Nd-based diene rubbers has been investigated since the 

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Functional homopolymers can be synthesized by essentially two different methods. The first and more preferred way is to use a functional initiator which will ensure a high rate of chain end functionality. For instance, the polymerization of St initiated by a unimolecular terpyridine-functionalized nitroxide initiator yields well-defined PS homopolymers. The second technique is based on post-polymerization modifications. In this case, the reaction between mPEG and chloroterpyridine yields terpyridine-functionalized PEG building blocks, as illustrated in Scheme 13. 

These possibilities are shown in Figure 1.15 and each will have a major effect on the chemorheological properties of the polymer compared with the linear parent. The detailed chemistry and mechanism of the reactions that lead both to linear polymers and to these different architectures are discussed in this section. The route to achieve these structures may involve stepwise polymerization addition polymerization, or post-polymerization modification. Each of these polymerization reactions, with particular emphasis on the way they may be adapted to reactive processing and the chemorheological consequences, is considered separately. Further detailed architectures such as graft and block copolymers with several different chemical components are then considered. 

Spirocyclic [l]ferrocenophanes have also been shown to thermally polymerize and these species function as cross-linking agents that allow access to PFSs with controlled cross-link densities2 Amber, solvent-swellable gels are available via this route (see Section 12.06.3.3.2). The [l]dichlorosilaferrocenophane 74 provides a very useful precursor to [l]ferrocenophanes 75 with alkoxy (or amino) substituents and subsequent ROP allows access to, for example, polyferrocenylalkoxysilanes 76 (Equation (31)). In addition, polymers with Si-H or Si-Gl groups have been prepared and these provide opportunities for post-polymerization modification via hydrosilylation and nucleo-... 

Post-polymerization modification is the most expensive method for preparing functional polymers. It is expensive because it means added steps. However, it is the method of choice when one wants to directly compare structure and reactivity or properties of functional with nonfunctional polymers. The only caveat is that chemical mo fication of polymers must not introduce adventitious chain scission or crosslinking. The other benefit of post-polymerization modification is that it can be accomplished for bulk polymers, as well as polymer surfaces. For some applications surface modification wUl be enough to achieve the desired effect... 

The limitations imposed by the incompatibility of certain monomer/ substrate combinations or the lack of a suitable monomer can be overcome by the post-polymerization-modification strategy, which serves to enlarge the range of obtainable functionalities. Furthermore, modifications of the grafted polymer are possible with reagents that cannot... 

Recently, we explored strategies for binding spiropyran moieties to structured brushes grafted from ETFE and Teflon (PTFE) surfaces in order to obtain light-sensitive structured polymer surfaces [18]. We focused on post-polymerization modification of grafted brush structures because this strategy increases the flexibility with respect to the optimization of the concentration of spiropyran moieties in the brushes. Moreover, the tedious synthesis and purification steps of spiropyran—monomer conjugates are circumvented. 

Scheme 30.3 The post-polymerization modification of hetero-bifunctional PS via consecutive thiol-ene and CuAAC coupling reactions. The identical click product is obtained from both reaction pathways. Adapted from Ref [49].

Scheme 30.5 The post-polymerization modification of PNIPAM prepared by RAFT polymerization by sequential aminolysis/Michael addition and thiol-ene click coupling. Adapted from Ref. [55].

Figure 31.4 The three distinct methods through which carbenes have been utilized for polymer synthesis. Type 1 Carbenes are essential to the polymerization process Type 2 Carbenes as side-group functionalities or reagents for post-polymerization modification Type 3 Carbenes are used as catalysts or ligands for polymerization catalysts.

Synthesis and post-polymerization modifications of aliphatic poly(car-bonatejs prepared by ring-opening polymerization 13CSR1312. Triazole-based one-dimensional spin-crossover coordination polymers 12CEJ15230. 

However, there seems to be a change in judging the situation and due to the development of new techniques, such as highly efficient post-polymerization modification techniques such as dick chemistry. The recent state in the field of terpenes, terpenoids, and rosin has been reviewed. These t5q>es of biomass are of low cost, and have much potential for their utilization as organic feedstocks for green plastics. 

PPEs can be prepared using a variety of synthetic routes polycondensation (including transesterification and polyaddition), ring-opening polymerization (ROP), and post-polymerization modification (Scheme 6.2). Each of these techniques has advantages and limitations, which make them suitable... 

Nevertheless, most of the work reported on the post-polymerization modification of poly(all lene H-phosphonate)s concerns the functionalization with reactive pendant groups that include hydroxyl or amino groups, which make possible the introduction of a wide range of (bio)ac-tive molecules and leading to new reactive PPEs with tunable properties for biomedical applications. Most of the post-polymerization functionalization methods involve the corresponding polymeric chlorophosphite, since it was early demonstrated that cyclic allgrlene chlorophosphites such as 2-chloro-2-oxo-l,3,2-dioxaphospholane cannot be polymerized efficiently. ... 

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