Step-growth polymerization system: A-End B-B B-End Α A A3 A₁ B₂ B₁₁ Moles of molecules: NA3,0 NA1,0 NB2,0 = 1.5 NA3,0 NB1,0 = NA1,0 Moles of A/B groups: 3NA3,0 NA1,0 2NB2,0 = 3NA3,0 NB1,0 = NA1,0

Chemistry
10th Edition
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
Section: Chapter Questions
Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...
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Monofunctional small-molecule carbamates ( 1 urethane bond per molecule) are used to deconstruct crosslink polyurethane (form by a stoichiometric mixture of difunctional isocyanate and trifunctional alcohols) via urethane bond exchange reactions (see Scheme below). Based on the reverse of the lory-Stockmayer "gelation" theory discussed in class, determine the amount of small-molecule carbamate decrosslinkers required to deconstruct crosslinked polyurethane (i.e., determine the mol% of the urethane bonds in small-molecule carbamate decrosslinkersrelative to the total urethane bonds in small-molecule carbamate decrosslinkers+crosslinked polyurethane, at which crosslinked polyurethane deconstructs). Hint: Small-molecule carbamate decrosslinker can be treated as a mixture of monofunctional alcohols (example A1) and monofunctional isocyanates (example B1) at full functional group conversion (i.e., P=1 ), while crosslinked polyurethane can be treated as a stoichiometric polymerization mixture of trifunctional alcohols (example A3) and difunctional isocyanates (example B2) at functional group conversion (i.e., P=1 ). The Problem 1 statement above is equivalent to asking "What is the minimum fraction of A groups that initially belong to A1 in the A3+A1 mixture in order for the A3+A1+B2+B1 polymerization system below to NOT gel even at full functional group conversion? [Reasonable assumptions can be made]

 

Step-growth
polymerization
system:
A-End
B-B
B-End
Α
A
A3
A₁
B₂
B₁₁
Moles of molecules:
NA3,0
NA1,0
NB2,0 = 1.5 NA3,0
NB1,0 = NA1,0
Moles of A/B groups:
3NA3,0
NA1,0
2NB2,0 = 3NA3,0
NB1,0 = NA1,0
Transcribed Image Text:Step-growth polymerization system: A-End B-B B-End Α A A3 A₁ B₂ B₁₁ Moles of molecules: NA3,0 NA1,0 NB2,0 = 1.5 NA3,0 NB1,0 = NA1,0 Moles of A/B groups: 3NA3,0 NA1,0 2NB2,0 = 3NA3,0 NB1,0 = NA1,0
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