Benzocyclobutene polymers

In the late 1970s, Kirchhoff at Dow Chemical Company developed the use of benzocyclobutenes in polymer synthesis and modification. These efforts culminated in 1985 with the issuance of the first patent describing the use of benzocyclobutene in the synthesis of high-molecular-weight polymer.27 Similar work that involved a thermosetting system based on Diels-Alder cycloaddition between terminal benzocyclobutene and alkyne groups,28,29 was reported separately and independently by Tan and Arnold.28 Since these initial discoveries, the field of benzocyclobutene polymers has expanded rapidly and benzocyclobutene chemistry constitutes the basis of a new and versatile approach to the synthesis of high-performance polymers for applications in the electronics and aerospace industries.30... 

Electronic coatings BCB Ultrem, Siltrem Benzocyclobutene polymers Polyimides Dow, USA GE-Plastics, USA... 

Benzocyclobutene polymers 5 100 0.5 Wafer coatings producer is backward-integrated... 

Table 17. Thermal properties of acetylenic benzocyclobutene Polymers...

Tan et al. investigated polymers made from bis-benzocyclobutenes [13-15]. As the benzocyclobutane is analogous to tbe dien, tbe Diels-Alder addition takes place. This reaction is applied to the preparation of polyimides. The advantage of this system is that the resultant polymer is oxidized to form thermally stable aromatic polyimides (Fig. 7). 

Some other PFs end capped with cross-linkable groups, such as benzocyclobutene, have been patented by Dow Chemicals [275-277]. For example, the thermal curing of spin-coated polymer 232 gave an insoluble pinhole-free film without alteration of the fluorescent properties (Chart 2.57). 

The synthesis and proposed cure mechanisms of this resin are described in reference 2. While the cure mechanism of the BCB terminated resin is not yet known, it is speculated that it reacts via one of two different routes. Initially the strained four member ring of the benzocyclobutene undergoes a thermally Induced ring opening. The opened rings then react with one another by a linear type addition to form a network type of structure or by cycloaddition to form linear polymer chains. An Illustration of the proposed polymerization mechanism of benzocyclobutene (BCB) terminated resins is shown below. 

The Diels-Alder reaction mechanism is discussed in greater detail in reference 3. As seen above the reaction between a benzocyclobutene terminated resin and a BMI results in the formation of linear polymer chains. 

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