CHEM 453: Polymer Chemistry Test Yourself Study Notes

Part I: Multiple Choice Questions

  • Question 1: According to the structural classification of polymers, which type of architecture is primarily responsible for the irreversible hardening seen in thermosetting plastics?

    • Answer: C) Chains chemically tied together to form a 3D network.

  • Question 2: In step-growth (condensation) polymerization, at what stage of the reaction does high molecular weight polymer typically form?

    • Answer: C) Only at the very end of the reaction (>99% conversion).

  • Question 3: Which of the following is a defining characteristic of polyanhydrides that makes them ideal for controlled drug delivery applications, such as Gliadel wafers?

    • Answer: B) They undergo surface erosion, dissolving layer-by-layer for steady release.

  • Question 4: Polyurethanes are often synthesized to form flexible or rigid foams. What is the chemical basis for this foaming action?

    • Answer: B) The reaction of the isocyanate group with water to release CO2 gas.

  • Question 5: Which of the following sets of monomers would yield a fully aromatic polyamide (Aramid) such as Kevlar?

    • Answer: C) p-Phenylenediamine and Terephthaloyl chloride.

  • Question 6: The etymology of the word "polymer" comes from the Ancient Greek words polus and meros. What does "meros" literally translate to?

    • Answer: B) Part or share.

  • Question 7: When synthesizing a polyanhydride carrier for a Gliadel wafer (Polifeprosan 20), what is the exact molar ratio of the hydrophobic shield (CPP) to the hydrophilic endogenous fatty acid (Sebacic Acid)?

    • Answer: B) 20:80.

  • Question 8: Which transition metal catalyst is classically associated with the oxidative coupling polymerization of 2,6-dimethylphenol to form Polyphenylene Oxide (PPO)?

    • Answer: B) Copper (I).

  • Question 9: In the synthesis of polysulfides (e.g., Thiokol), the condensation of an organic dihalide with a sodium polysulfide yields the polymer and what small molecule byproduct?

    • Answer: D) Sodium chloride.

  • Question 10: Which polymer class is known as the "Chameleon of Polymers" because it undergoes step-growth polymerization but does NOT release a small molecule byproduct?

    • Answer: B) Polyurethane.

  • Question 11: Which architectural term describes a copolymer with the general structure [- A-A-A-B-B-B-]?

    • Answer: C) Block.

  • Question 12: You can classify the producing of Dacron and Kodel polymers as:

    • Answer: F) B & D (Copolymers and Step growth).

Part II: Short Answer Questions

  • Question 1: Explain why Nylon-6,6 exhibits high crystallinity and toughness, making it suitable for gears and ropes.

    • Answer: Nylon-6,6 owes its strength and crystallinity to strong intermolecular hydrogen bonding between the C=O and N-H groups of adjacent polymer chains.

  • Question 2: In the synthesis of Polyethylene Terephthalate (PET), what conditions are used and why?

    • Answer: High heat (>250ºC), high vacuum, and inert nitrogen gas purge are employed. This drives the equilibrium forward, as water is released during condensation and can cause hydrolysis if retained. Heat keeps water in gas phase, and vacuum removes this vapor, promoting high molecular weight polymer.

  • Question 3: Identify the structural feature of polysulfides (like Thiokol) that provides their unique stress relaxation capabilities.

    • Answer: The sulfur-sulfur (-S-S-) bridge allows the polymer to rearrange bonds under stress, enabling it to relax without cracking. They show high resistance to non-polar solvents like gasoline, jet fuel, crude oil, and UV light.

Part III: Compare and Contrast

  • Compare between: Polyurethane and Polyurea

    • Reactants:
    • Polyurethane uses a Diol;
    • Polyurea uses a Polyamine.
    • Reaction Speed:
    • Polyurea is extremely fast (cures in 3-10 seconds);
    • Polyurethane is slow to moderate.
    • Moisture Sensitivity:
    • Polyurethane reacts with moisture to form CO2, causing foaming;
    • Polyurea has low sensitivity and can be applied to wet surfaces.

  • Compare between: PET and PBT

    • Chemical Structure Difference:
    • PET has an ethylene group between ester linkages;
    • PBT has a butylene group.
    • Applications:
    • PET is used in packaging (beverage bottles, food trays);
    • PBT is used for electronic parts (relays, switch housings).

  • Compare between: Kevlar and Nomex

    • Isomerism:
    • Nomex is the meta-substituted aramid;
    • Kevlar is the para-substituted aramid.
    • Applications:
    • Nomex is used for flame-resistant clothing;
    • Kevlar is used for bullet-proof clothing.

Part IV: Complete the Reactions

  1. Polycarbonate Synthesis:

    • Reactants: Bisphenol A + Phosgene
    • Predicted Products: Polycarbonate + HCl.

  2. Nylon-6,10 Synthesis:

    • Reactants: Hexamethylene diamine + Sebacoyl chloride
    • Predicted Products: Nylon-6,10 + HCl.

  3. Polyurethane Synthesis:

    • Reactants: Diisocyanate (OCN-R-NCO) + Diol (HO-R'-OH)
    • Predicted Products: Polyurethane + CO2 (from water).

  4. Polyethylene Adipate Synthesis:

    • Reactants: Adipic Acid + Ethylene glycol
    • Predicted Products: Polyester + Water.

  5. Flexible Polyurethane Foam:

    • Reactants: Isocyanate + Water.
    • Predicted Products: Polyurethane Foam + CO2.

  6. Ethylene glycol + Phthalic anhydride:

    • Predicted Product: Linear polyester.

  7. Maleic anhydride + Alcohol:

    • Predicted Product: Unsaturated polyester.

  8. Ethylene glycol + Terephthalic acid:

    • Predicted Product: PET + Water.

Part V: Problem-Solving & Application

  1. Glyptal Polyester Synthesis:

    • Phase Change Explanation:
      • Remains linear at low conversions (<70ºC); becomes cross-linked at high conversions due to hydroxyl reactivity. Primary hydroxyls react first forming chains. Higher conversions lead to secondary hydroxyl reactions forming cross-links.

  2. Gliadel Wafer Formulation:

    • Adjusting Molar Ratio: Increase hydrophobic CPP to slow drug release. This hinders water penetration, extending release profile.

  3. Polyether Properties:

    • Specific Linkage: -C-O-C- (ether linkage) allowing flexibility and preventing tight packing unlike esters or amides.

Part VI: Polymer Classification

  1. Classification by COMPOSITION:

    • A) Block Copolymer
    • B) Alternating Copolymer
    • C) Graft Copolymer
    • D) Homopolymer
    • E) Random Copolymer

  2. Classification by STRUCTURAL Architecture:

    • A) Linear Polymer
    • B) Cross-linked / Network Polymer
    • C) Branched Polymer

  3. Functionality of Monomers:

    • A) Linear Polymer
    • B) Cross-linked Polymer

  4. Classification by SOURCE:

    • A) Natural Polymer (Cellulose)
    • B) Synthetic Polymer (Polyethylene)
    • C) Natural Polymer (Silk)
    • D) Natural Polymer (DNA)
    • E) Synthetic Polymer (Nylon)
    • F) Natural Polymer (Keratin)
    • G) Natural Polymer (Starch)
    • H) Synthetic Polymer (Synthetic Rubber).

  5. Match Polymers to Chemical Family:

    • 1: C) Polycarbonate
    • 2: E) Polyether (PEEK)
    • 3: D) Aramid
    • 4: B) Polyester
    • 5: A) Polysulfide.

  6. Match Polymers to Monomer Units:

    • 1: C) Butylene glycol + Terephthalic acid
    • 2: D) 2,6-dimethylphenol
    • 3: A) Ethylene glycol + Adipic acid
    • 4: F) p-phenylenediamine + terephthaloyl chloride
    • 5: B) Hexamethylenediamine + Adipic acid
    • 6: E) Caprolactam.

  7. Structural Classification of Specific Polymers:

    • A) Glyptal: Cross-linked Network; Copolymer.
    • B) PPO: Linear; Homopolymer.
    • C) PET: Linear; Copolymer.