MRG QuickNotes ©1998

Microcal Origin: The Fun of Number Crunching (or Calculating [h])

Tour Guide: Leslie White

(This QuickNote was designed for use with Microcal Origin version 4.1. If another version is used, your mileage may vary)

M Do not turn PC off.

MM Do not change any of the program or computer default settings.

MMM NEVER Download anything to the polymer science computers.

1. Select 'New' under File menu, then 'Project'. A data worksheet with 2 columns will appear on the screen

2. Select 'add new columns' under the Columns menu. A prompt will appear for the number of columns to add . . . type in 2

3. Type the numbers obtained during the lab for flow times in the columns (each time for a single concentration will read across in a row rather than down in a column).

4. After entering the flow times for each of the polymer solution concentrations, highlight all columns with the mouse and select 'statistics on rows' under the Analysis menu.

5. The average flow time for each polymer concentration has now been calculated. This number is found in the mean(Y) column. Highlight this column.

6. Under the analysis menu, select 'normalize'. When prompted for a number, enter the flow time for solvent. The values in the mean(Y) column now represent h_r. Highlight this column using the mouse. Double click on this column and at the prompt, rename it as Nrel. This will make it easier to keep up with which column is which down the road . . . trust me.

7. Select 'add new columns' under the Columns menu. At the prompt, add one new column then highlight it. Under the Column menu, select 'set column values'. At the prompt, enter col(Nrel)-1. Click on the button marked 'do it'. This column now represents h_sp. Doubleclick the highlighted column and rename as Nsp.

8. Select 'add new columns' under the Columns menu. At the prompt, add two new column. Enter the values for the polymer solution concentrations in the first new column. Double click on the highlighted column to rename as con

9. Highlight the second new column using the mouse. Under the Column menu, select 'set column values'. At the prompt, enter col(Nsp)/col(con). This column now represents h_red. Double click on this highlighted column and rename Nred. Now unhighlight all columns.

10. Under the Plot menu, select 'scatter'. A list of all columns will appear. Click on the column mark 'con'. Click on the <->X button found to the immediate right of the box that lists the columns. Now click the column marked 'Nred'. Click on the <->Y button found to the immediate right of the box that lists the columns. This sets the x and y values for the linear plot.

11. Click on OK to plot this data (h_red vs con). Another window, Graph1, will open.

12. Under the analysis menu, select 'fit linear'. A script window will appear that contains the linear regression data. The y-intercept is [h]. The slope is a k'[h]².

13. Now click back on the data worksheet and create yet another new column (add new column under the column menu)

14. For the new column, 'set column values' as ln(col(Nrel))/col(con). Rename this column as Ninh. This is the inherent viscosity.

15. Now click back on graph1. Under the plot menu, select 'add plot to layer' and 'scatter'. Set the concentration column as the x value, and the Ninh column as the y-value

16. Under the data menu, select the proper data set, (con, Ninh).

17. Under the analysis menu, select 'fit linear'. A script window will appear that contains the linear regression data. The y-intercept is [h]. The slope is k"[h]²

18. If the moon and stars were in the proper alignment when the experiment was done, the two y-intercepts, the intrinsic viscosity, for both lines will be the same. k' - k" will equal 0.5. The intrinsic viscosity that was calculated can now be used in the Mark-Houwink equation to give the molecular weight of the polymer.

19. The x and y axis on the graph produced can be renamed by double clicking on them. The same goes for the legend as well as for rescaling the axes.