Controlled polymerization method

There are already several excellent detailed reviews on GTP [2-5]. In this chapter I will critically analyze the existing data that strongly support a dissociative (anionic) mechanism originally proposed by R. Quirk of Akron University [6]. I will also explain how GTP can operate at 80 °C when it is well known that the classical anionic polymerization of methacrylates does not proceed above ambient temperatures. In addition, GTP will be compared to other controlled polymerization methods. 

To fully exploit the beneficial properties of PIB in, for example, polyurethanes, thermoplastic elastomers, and sealants, controlled polymerization methods are required that provide access to controlled end-group functionalities. The controlled polymerization of isobutene was first reported by Kennedy, which was based on the inifer technique. This so-called inifer that is added to provide control over the polymerization is a compound that acts both as the initiator and the transfer agent. The inifer deliberately induces chain transfer to control the molecular weight of the PIB, whereby each transfer step generates... 

The most important achievement of living /controlled polymerization methods and techniques is the synthesis of tailor-made block copolymers with specific macromolecular architecture, chemical composition/functionality, low molecular polydispersity, and corresponding minimized heterogeneity. 

Figure 8 Main mechanistic transformation reactions in living and/or controlled polymerization methods. ATRP, atom transfer radical polymerization RAFT, reversible addition-fragmentation chain transfer NMRP, nitroxide-mediated free radical polymerization CROP, cationic ring-opening polymerization AROP, anionic ring-opening poiymerization.

The stereochemistry of polymer chains often significantly controlled polymerization methods and molecular designs. 

The development of controlled polymerization methods for the ring-opening polymerization of NCAs by the groups of Deming, Schlaad, and Hadjichristidis has intensified research in the field of block copolymer hybrids containing homopolypeptide fragments. " ... 

In this article, block copolymers prepared by controlled polymerization methods only are considered, primarily di- and triblock copolymers. Multiblock copolymers such as poly(urethanes) and poly(urethane-ureas) prepared by condensation polymerization are not discussed (see Polyurethanes (PUR)). Although these materials do exhibit microphase separation, it is only short range in spatial extent due to the high polydispersity of the pol5uners. 

Synthetic carbohydrate polymers, the so-called glycopolymers , have been prepared over the last years by using controlled polymerization techniques, as these techniques not only allow precise control of the polymerization process but also enable access to precise polyvalent arrangements containing a variety of functionalities [38-40]. Among the controlled polymerization methods, ROMP has attracted considerable attention [41]. 

Furthermore, these block copolymers may be designed to contain stimuli-responsive components such that the assembly process may be triggered through the application of a stimulus. With unique properties and a host of potential applications, stimuli-responsive assemblies such as micelles, vesicles, bioconjugates, films, networks, and patterned surfaces have been prepared from block copolymers synthesized via controlled polymerization methods (Fig. 3.5) [1, 42]. 

Christo B. Tsvetanov is full professor of polymer science at the Institute of Polymers, Bulgarian Academy of Sciences and head of the Scientific Council of the Institute of Polymers. A major focus of his research concerns controlled polymerization methods, water-soluble polymers and hydrogels, stimuli-responsive copolymers, and their self-assembly to polymeric nanopartides. He is well known for his contributions to the area of anionic coordination polymerization ofoxiraneandthe role of donor and acceptor additives on the mechanism of anionic polymerization. Since 2004, he has been a corresponding member of the Bulgarian Academy of Sdences. 

The development of PPE synthetic chemistry makes the synthesis of PPEs with various structures possible. Recently, PPE-based polymers with different topological structures including linear random copolymers, block copolymers, star polymers, miktoarm polymers, and brush and hyperbranched polymers have been synthesized. Among them, linear homopolymers or random copolymers of PPEs are perhaps the most studied. Different block copolymers with AB, ABA, and ABC architectures have been synthesized by controlled ROP. By the combination of ROP of PPE with other controlled polymerization methods, such as living radical polymerization, or click chemistry, more complex architectures including miktoarm, comb, or graft copolymers can be synthesized. The richness of structures has allowed the convenient adjustment of material properties of PPE for biomedical applications. 

Polymerization, recently reviewed" ) only pertains to the use of cobalt and is not spedfic for the reversible deactivation mechanism vide infra). The term OMRP covets aU metals. The use of this aaonym was initially limited to the reversible deactivation mechanism outlined in Figure 1. However, it has recently been shown that organometallic compoimds may also act as transfer agents for the controlled radical polymerization that follows the degenerative transfer prindple, as outlined later in Section 3.11.4. In this chapter, both these two controlled polymerization methods, which may in certain cases interplay, will be outlined. When addressing each specific mechanism, an additional qualifier will be added to the acronym, OMRP-RT for reversible termination and OMRP-DT for degenerative transfer, whereas the OMRP term will be used in a more general situation. 

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