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Eric Echeandia Prof. Yan Meng General Chemistry Lab (Tuesdays: 1:30-4:30) 15 March 2017 Lab report

Calculations 1. Describe the appearance of the polystyrene that you made. Describe the appearance of the Glyptal resin. Compare the properties of Glyptal with those of polystyrene. a. The polystyrene was yellow, solid, hard and crystal-like. The glyptal resin was yellow, opaque, crystal-like and hard. Both of these polymers had very similar appearances. Also, both were able to be grinded and pulverized into powder. Although both look similar, the polystyrene is insoluble in both water and acetone. On the other hand, the glyptal resin was soluble in acetone and insoluble in water. 2. Describe the changes in bonding and hybridization of the carbon atoms that take place during the polymerization of styrene to form polystyrene. a. During this reaction, lower energy bonds are created, to form a more stable polystyrene molecule. In this reaction, what happens is that the top double CHCH2 bonds are rearranged and result in weaker CH-CH2 single bonds. Each styrene molecule is hybridized and the more stable polystyrene is formed. 3. Summarize the various effects which you observed cross-linking to have on the properties of a polymer. a. Cross-linking is when long chains of polymers join together through covalent bonds. When this happens, the polymer becomes irreversibly hardened. This could be observed in this experiment. For example, when forming glyptal resin, where the product ends up being irreversibly hard and solidified. Another instance where we observed cross-linking was with the glue, borax and water. When these were cross-linked, the product ended up being irreversibly solidified. Also, because the of the covalent bonds formed, the product ended up being very hard to separate. In the end, cross-linking produces more solid, hardened, unified, and stronger products. 4. Calculate the mole ratio for the reactants used in the Glyptal resin preparation: numbers of moles phtalic anhydride number of moles glycerol

glycerol: 92.09 g/mol; density = 1.261 g/mL phthalic anhydride: 148.12 g/mol 5.00 g phthalic anhydride =0.0338 mol phthalic anhyride g 148.1 phthalic anhydride mol (1.262g/mL of glycerol) (2 mL of glycerol) = 2.522 g glycerol 2.522 g of glycerol =0.0274 mol glycerol g 92.09 of glycerol mol mole ratio :

0.0338 mol phtalic anhydride 0.0274 mol glycerol

=1.234 moles

Should the mole ratio for this crosslinked polymer be greater than, less than or equal to 1? Explain. Because more moles of phtalic anhydride were utilized, then the mole ratio should more than 1. 5. Describe what you observed when different amounts of water and borax solution were used in preparing the cross-linked polymer from glue. Name two or three properties which you feel would be desirable to have in this polymer, and what recipe you would use to obtain this “best” polymer. a. In the original try for this part of the experiment, we used 15mL of water and 10mL of borax. This led to a cross-linked polymer that was slimy, white, and stretchy. When left to rest, the polymer would stretch out in the surface. When I modified the formula, I added 5mL of water and 15mL of borax. This les to the polymer being less bouncy, stickier, white, and not stretchy. When observing the other students’ modifications, when they added more borax, the polymer was more compact and less stretchy. When they added more water, the polymer was similar to the product of the original try. I think that the most desirable properties of this polymer would be the stretchiness, stickiness, ability to attach to surfaces and spread out, among others. According to the observations from my peers’ work, I concluded that the best formula was 10mL of water and 5mL of borax. 6. What are some possible commercial uses for sodium polyacrylate? Provide an explanation for what happens to the expanded polymer after salt is added to it. a. Some commercial uses for sodium polyacrylate are in diapers and detergents. Because this polymer is able to absorb a lot of water, it is used in diapers to absorb the fecal matter and its odors in babies. For the detergents, it has the ability to bind multiple hard-water elements, making the detergent more effective.

b. When salt was added to the polymer, the polymer returned to being more liquid and moveable. This happened because in the presence of NaCl, water feels more attracted to this ionic compound. The water left the polymer, which caused the polymer to collapse, returning to a more liquid state. 7. Could ethylene glycol (structure shown) form a condensation polymer with phthalic anhydride in the same way that glycerol does? Explain. a. No, they would not be formed in the same way. If ethylene glycol reacts with phthalic anhydride it would be a linear polymer. Whereas if ethylene glycol reacts with glycerol, it would be a more complex, highly branching polymer. This has to do with the OH groups in ethylene glycol and in glycerol....