Abstract
1H NMR and 13C NMR spectrometry (1-dimensional and 2-dimensional) have been used to assign chemical resonances and determine the degrees of branching for polyesters synthesized by the Lewis acid (dibutyltin(IV)oxide)-catalyzed polycondensation of glycerol with either succinic acid (n (aliphatic chain length) = 2), glutaric acid (n = 3) or azelaic acid (n = 7) in quasi-melt solutions with toluene. When 1:1 and 2:1 (diacid:glycerol) molar ratios were used, it was found that the glutaric acid-derived polymers gave the highest degree of polymer branching (31.2%, 85.6%, respectively) after the 24 h reaction period followed by the succinic acid-derived polymers (39.4%, 41.9%, respectively) and the azelaic acid-derived polymers (9.9%, 13.9%, respectively). Reactions performed at reflux for 24 h resulted in a 70.8% and 56.7% decrease in degree of branching for succinic acid and glutaric acid-derived polyesters, respectively. There is no indication that degree of branching is significantly affected by the presence or absence of solvent according to the results obtained in this research.
Highlights
Degree of branching (D.B.%) has been well studied in systems that involve the direct condensation reaction between difunctional A2 monomers, such as diacids, and trifunctional B3 monomers, such as Polymers 2012, 4 glycerol, in the presence of lipase and chemical catalysts to form hyperbranched polymers [1,2,3,4,5,6,7].Understanding the relationship between D.B% and the physical and chemical properties of hyperbranched polymers is necessary to identify potential applications
The 1H and 13C Nuclear Magnetic Resonance (NMR) resonance peaks associated with these units can be integrated and used to calculate the degree of branching according to Equation (1) [2,3,6,13,17,22,23,24]
H NMR and 13C NMR (1-dimensional and 2-dimensional) has been used to successfully assign and integrate chemical resonances and determine the degrees of branching along the glycerol backbone of polyesters synthesized from glycerol and diacids in the presence and absence of toluene
Summary
Degree of branching (D.B.%) has been well studied in systems that involve the direct condensation reaction between difunctional A2 monomers, such as diacids, and trifunctional B3 monomers, such as Polymers 2012, 4 glycerol, in the presence of lipase and chemical catalysts to form hyperbranched polymers [1,2,3,4,5,6,7].Understanding the relationship between D.B% and the physical and chemical properties of hyperbranched polymers is necessary to identify potential applications. Degree of branching is a structural property that is determined by the concentration of linear (L), terminal (T) and dendritic (D). Dendritic (treelike) macromolecules, dendrimers and hypebranched polymers, have received much attention in recent years because their highly branched structures and large number of terminal functional groups are expected to produce materials with unique properties when compared to their linear analogues [8,9,10]. There are no unreacted functional groups or linear units along the branched chains of dendrimers. Hyperbranched polymers are prepared by one-pot processes whereby difunctional (A2) and trifunctional (B3) monomers are reacted at random yielding products with 15–90% branching [6,11,12,13,14]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
