Functional groups functionalized polymer

In addition to providing fully alkyl/aryl-substituted polyphosphasenes, the versatility of the process in Figure 2 has allowed the preparation of various functionalized polymers and copolymers. Thus the monomer (10) can be derivatized via deprotonation—substitution, when a P-methyl (or P—CH2—) group is present, to provide new phosphoranimines some of which, in turn, serve as precursors to new polymers (64). In the same vein, polymers containing a P—CH group, for example, poly(methylphenylphosphazene), can also be derivatized by deprotonation—substitution reactions without chain scission. This has produced a number of functionalized polymers (64,71—73), including water-soluble carboxylate salts (11), as well as graft copolymers with styrene (74) and with dimethylsiloxane (12) (75). 

The anionic polymerization of methacrylates using a silyl ketene acetal initiator has been termed group-transfer polymerization (GTP). First reported by Du Pont researchers in 1983 (100), group-transfer polymerization allows the control of methacrylate molecular stmcture typical of living polymers, but can be conveniendy mn at room temperature and above. The use of GTP to prepare block polymers, comb-graft polymers, loop polymers, star polymers, and functional polymers has been reported (100,101). 

Sihcone polymer plasticizers have historically been used in many formulations. These plasticizers (qv) are of the same Si—O backbone as the functional polymers but generally are terrninated with trimethyl groups which are unreactive to the cure system. This nonreactivity means that, if improperly used, the plasticizer can migrate from the sealant and stain certain substrates. Staining has been a widely pubHcized flaw of sihcone sealants, but the potential of a formulation to stain a substrate can be minimized or eliminated with proper formulation work. In general, this is accompHshed by not using plasticizers for formulations developed for stain-sensitive substrates. 

Functional groups on polymer and polymer film surfaces... 

Covalent crosslinking. Acrylic polymers can be covalently crosslinked through direct reaction between functional monomers in the polymer itself or by the addition of a crosslinking reagent, which typically reacts with the functional groups or polymer backbone in the PSA. In general, acrylic polymers are very... 

We have studied, by MD, pure water [22] and electrolyte solutions [23] in cylindrical model pores with pore diameters ranging from 0.8 to more than 4nm. In the nonpolar model pores the surface is a smooth cylinder, which interacts only weakly with water molecules and ions by a Lennard-Jones potential the polar pore surface contains additional point charges, which model the polar groups in functionalized polymer membranes. 

In the case of functional polymers such as nylon, the molecular size can increase because ionic functional groups contained in the molecule repel each other. To decrease ionic repulsion, sodium trifluoroacetate should be added to HFIP. 

G. S. Kumar, Azo Functional Polymers—Functional Group Approach in Macromolecular Design, Tech-nomic Publ., Lancaster (1989). 

In addition, there are many surface modification processes that use triplet sensitizers to permit oxidation reactions. In a typical process, polyisocyanate is applied on a polyolefin together with a sensitizer such as benzo-phenone and then irradiated with UV light. As shown in Eq. (15) the sensitizer has an oxidizing effect to produce hydroxyl groups over the polymer surface. These hydroxyl groups finally react with isocyanate to provide a functional polymer [56,57]. 

The polyelectrolyte covalently functionalized with reactive groups may be viewed as an enzyme-like functional polymer or as a molecular reaction system in the sense that it has both reactive centers and reaction rate-controlling microenvironments bound together on the same macromolecule. 

Postelnek,W., Colemann, L. E., and Lovelace, A. M. Fluorine-Containing Polymers. I. Fluorinated Vinyl Polymers with Functional Groups, Condensation Polymers, and Styrene Polymers. Vol. 1, pp. 75— 113. 

I. Fiuorinated Vinyl Polymers with Functional Groups, Condensation Polymers, and Styrene Polymers. Vol. 1, pp. 75-113. 

General aspects of chain transfer have been reviewed by Chiefari and Rizzardo,3 Barson, 1 Farina/ Fastmond6 and Palit el al1 The use of chain transfer in producing lelechelic and other functional polymers has been reviewed by Boutevin,8 Heitz/ Comer10 and Starks11 and is discussed in Section 7.5.2. There are two main mechanisms which should be considered in any discussion of chain transfer (a) atom or group transfer by homolytie substitution (Section 6.2.2) and (b) addition-fragmentation (Section 6.2.3). 

Group transfer processes are of particular importance in the production of telechelic or di-end functional polymers. 

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 thiocarbonylthio group can be transformed post-polymerization in a variety of ways to produce end-functional polymers or it can be removed. The presence of the thiocarbonylthio groups also means that the polymers synthesized by RAFT polymerization are usually colored and they possess a labile end group that may decompose to produce sometimes odorous byproducts. Even though the color and other issues may be modified by appropriate selection of the initial RAFT agent, these issues have provided further incentive to develop effective methods for treatment of RAFT-synthesized polymer to transform the thiocarbonylthio groups post-polymerization. 

Commercial end functional polymers have been converted to alkoxyamincs and used to prepare PKO-Worri-PS.040 The hydroxyl group of alkoxyamine 284 was used to initiate ring-opening polymerization of caprolactonc catalyzed by aluminum tris(isopropoxide) and the product subsequently was used to initiate S polymerization by NMP thus forming polycaprolactone-Wodr- P8.641 The alternate strategy of forming PS by NMP and using the hydroxyl chain end of the product to initiate polymerization of caprolactonc was also used. 

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. 

The key requirements for using Si-Cl functional initiators to produce polymers carrying Si Cl termini by carbenium ion polymerization are i) Si-Cl should be inert toward aUcylaluminum coinitiators, ii) Si-Cl should not react with propagating carbenium ions, in) chain transfer to monomer should be negligible so as to end up with one Si-Cl head-group per polymer chain. 

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. 

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