Discuss, Learn and be Happy חזרה לדיון

help brightness_4 brightness_7 format_textdirection_r_to_l format_textdirection_l_to_r

1) In free radical chain reaction polymerization of vinyl monomers, the rapid growth to high polymer molecular weight (MW) even at a low level of the total concentration of monomers polymerized, is due to which of the following? (Choose from the following four possibilities)

1
done
by
מיין לפי

Which of the following statements is true about monomer orientation as it adds to the propagating chain in the radical polymerization of mono-substituted vinyl compounds (H2C=CHR where R is a group or atom such as benzene, nitrile, chloride)? (Choose from the following four possibilities)

1
done
by
מיין לפי

Which of the following differences between polymers with chemical covalent crosslinks as compared to ionic and non-covalent crosslinks, is not correct? (Choose from the following four possibilities)

1
done
by
מיין לפי

If a condensation polymerization is carried out with a mixture of a tetra functional carboxylic acid and a difunctional carboxylic acid and a difunctional alcohol monomers where the alcohol and carboxylic acid groups are in equivalent molar amounts what will be the approximate reaction conversion, p, of monomers into polymer at the gelation point? (Choose from the following four possibilities)

1
done
by
מיין לפי

Which of the following can best be made by stepwise condensation or stepwise addition polymerization? (Choose from the following four possibilities)

1
done
by
מיין לפי

Which of the following statements on the rates of propagation (Rp) for vinyl chain reaction polymerization of ionic and free radical chain reaction polymerization is correct (Choose from the following four possibilities)?

1
mood
by
מיין לפי

The molecular weight of two different samples of a polymer of the same repetitive monomers, but made by different polymerization methods were measured by light scattering and membrane osmometry and the ratios of the MW from the light scattering vs. membrane osmometry for sample 1 was 1.4 and for sample 2 sample was 2.1. What conclusions can be made about the method of polymerization of polymer samples 1 and 2?

1
done
by
מיין לפי

In carrying out chain reaction living polymerization different amounts of the same initiator are used. In sample 1 one mole of initiator are used, in sample 2 four’moles of initiator are used and in sample 3 three mole of initiator are used. The monomer concentrations are kept the same in each case. Which sequence best expresses the relative magnitude of the different molecular weights?

1
done
by
מיין לפי

Polyesters made from cyclic lactones or from hydroxyl alkyl carboxylic (e.g. HO (CH2)5COOH acids have identical chemical structures but with significantly different molecular weights and molecular weight distribution. Which of the following statements about the polymers is correct? (Choose from the following four possibilities)

1
done
by
מיין לפי

In gel permeation chromatography for determining molecular weight distribution standard polystyrene polymers are used to calibrate the column. These polystyrene polymer samples are characterized by what type of molecular weight range and how are they generally synthesized? (Choose from the following four possibilities)

1
done
by
מיין לפי