Polymers, error-checking

Boronate ester formation has proven to be a facile alternative to traditional polymer assembly, given the ease of synthesis and dynamie reversibility to afford error-checking mechanisms during synthesis. Compared to conventional supramolecular polymers, boronate-linked materials display enhanced stability. It is argued that boronate ester formation takes the best from both worlds. 

As in the polyenes case, we can see that these values increase with the lengthening of the polymeric cMin. We observe the good agreement between our values and those obtained by Williams[12] for the three first compounds of the series, whereas for the higher polymers our values are lower. After checking of the calculations, it seems to us that an error could have occur in Williams computations. 

Values for system peak parameters were found using a narrow distribution polystyrene standard (PS68K) before calculating MWD data for the lignin samples from universal calibration. To check software and instrument operation, several narrow MWD polystyrene and one broad MWD polymethylmethacrylate standards were treated as unknown samples and subjected to analysis with the universal calibration curve assembled from all polymer standards files. It was found that the MWD could be estimated for the recalculated polymer standards with errors between 5 and 10% of the original value indicated by the supplier of the standard (e.g., Mw for PS11K and Mw and M for PMMA17K-6). 

To check the phase transformation isotropic -> nematic, the validity of the Clausius Clapeyron equation is examined. It has been shown 38), that within the experimental error the results fulfill Eq. 1 in analogy to the low molar mass l.c. The phase transformation isotropic to l.c. is therefore of first order with two coexisting phases at the transformation point. Optical measurements on the polymers confirm these thermodynamical measurements (refer to 2.3.1.3). 

The tests were performed to check how close the predictions from the master curve are to the actual data of viscosity versus shear rate. For most polymers, the error in the predicted value was limited to a maximum of 20%. The minimum deviation was less than 3%, as in the case of PET. For some polymers, however, the maximum mror in the case of some data was within a broader band of 40%. The reason for diis is that the master rheogram itself had a broad bandwidth. Because most of the data were coalesced from existing literature data, the errors in the miginal data naturally oeep into the predictions from the master curve. It is known fiiat, even with the most sophisticated equi ments, errors to the extent of S0% can oeq> in if proper care is not taken when generating the data. Thus, the blame for the broader error band in the case of some polymers, that too only in file low-medium shear-rate ran s, does not rest entirely with file master curve. If the original data which are used for forming the master curve are error-free, then automatically the master curve predictions would be very accurate, as fiie unification tedmique itself is very reliable. 

Quantitative analysis taking sample absorption and thickness into account Recently, the validity of Harrick s weak absorber approximations has been checked by comparison with the general thickness-and absorption-dependent model. It was found that the formalism depicted in the section above may be used for film thicknesses up to 20 nm. Especially if the film is in contact with a third bulk medium, e.g. water, the deviation between accurate and approximate calculation of relative electric field components according to Equation [29] was found to be below 3%, i.e. within the error of most experiments. A comprehensive description of ATR spectroscopy of polymers using the general formalism can be found in the Further reading section. 

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