Synthesis of aromatic benzoxazole polymers for high T, low dielectric properties/Title> - Polyimides and Other High Temperature Polymers - page 218

Figure 5. DSC scan of the model compound, 2,5-bis(2-benzoxazolyl)-1,4-di(allyloxy)benzene.

tance to the polymers through thermal cure of the allyl functionality was provided
by model compound chemistry. DSC characterization of the model compound
(Figure 5), 2,5-bis(benzoxazolyl)-1,4-di(allyloxy)benzene exhibited a clear trend.
It showed an endotherm from 224-226 ° C, which corresponded well with the cap-

illary melting point (222-223 ° C) of the model compound. This is followed by an

exotherm in the 225-275 C. This is presumably due to

the formation of the product of a Claisen rearrangement reaction of the starting
material. A second endotherm occurs at 298-301

° C range, centered at 244 °

C, which should presumably
correspond to the melting point of the new product. A final exotherm in the 303-
400

°

° C temperature range and centered at 345 ° C is attributable to the crosslinking

reaction of the allyl groups.
By analogy, the DSC scans of a candidate O-allyl-6F-12F (50/50) benzoxazole
copolymer (Figure 6) exhibit two distinct exotherms centered at 252 ° C and

363 C, attributable to thermal rearrangement of the phenylallyl ether and

crosslinking reaction, respectively. The T g of the cured polymer is 350

°

° C, as can

be seen by DSC.
Table 4 also summarizes the maximum temperatures for the exotherms that
correspond to the Claisen rearrangement, crosslinking reactions, the T g of the
thermally cured materials as well as the onset temperatures of degradation of the
aromatic benzoxazole homo- and copolymers containing monoallylether groups.
Also included in the Table are the thermal characteristics of the random triblock
copolymers which are partially allylated. High glass transition temperatures after