Chemical structure of di-block copolymer

The silicon wafer surface was prepared in the same manner as that for the cooperativity studies (see section 3.1.2.1). 

0% solution by weight was prepared by dissolving 50 mg of copolymer in 5.0 mL toluene. A clean silicon wafer was set onto the spin coater and four drops of solution were placed on the surface. Each polymer brush sample was rotated at 1000 rpm for 1 minute. 

To chemically bond the polymer chains to the silicon surface the polymer brush samples required heat well above their Tg s. All samples were placed in a vacuum oven (25 Torr) at 170°C immediately following spin coating. The terminal OH groups reacted with the native oxide layer of the silicon wafer as demonstrated in literature. The reaction time was varied by removing samples from the high temperature environment at 10, 20, 40, 100, and 200 hours. (Because the 200 hour sample results duplicated the 100 hour sample results, only results for the 100 hour sample are presented.) To remove any unreacted polymer, the samples were immersed in toluene and placed in a sonicator for a total of 34 hours at approximately 40°C. 

After the unreacted polymer was removed, the films were washed with toluene and chloroform to alter the chain comformations. Analysis was performed to observe 

Three major variables were investigated in this polymer brush study the initial reaction time of the sample, the solvent last used to wash the sample, and the effect of a hydrolysis reaction. As the samples are discussed, the number depicts the reaction time, the next letter represents the solvent (t, toluene c, chloroform), and a h indicates a hydrolyzed polymer. For example, 40ht means the sample has a reaction time of 40 hours, was last washed in toluene, and has been hydrolyzed. A complete listing of all the polymer brush samples prepared appears in Table 3.2-3. 

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Figure 3.2-2 Chemical structure of di-block copolymer after hydrolysis.

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