Distribution of dendritic, terminal and linear units and relationship between degree of branching and molecular weight of AB(2)-type hyperbranched polymer: A C-13-NMR study

作者：Shanmugam T; Raghavan A; Nasar A Sultan^*

来源：Journal of Macromolecular Science Part A-Pure and Applied Chemistry, 2006, 43(9): 1387-1397.

DOI：10.1080/10601320600820256

• C-13-NMR spectroscopy
• degree of branching
• hyperbranched polymers

Degree of branching (DB) of AB 2 -type hyperbranched polymer has been studied using C-13-NMR spectroscopy. For this purpose, a series of hyperbranched polyamides based on 3,5-bis(4-aminophenoxy)benzoic acid differing in molecular weight was prepared by adopting a fractional precipitation technique. A model compound mimicking exactly the terminal and dendritic units present in the hyperbranched polymer (HBP) was also synthesized in high yield. C-13-NMR spectra of the polymers and the model compound were recorded under exacting experimental conditions. With the help of C-13-NMR spectrum of model compound and the integration values, peaks for terminal (T) units, dendritic (D) units and linear (L) units present in the HBP have been assigned. The spectra of low molecular weight fractions clearly showed that the linear unit is first formed and then the dendritic unit. Plots of mole fraction of individual unit against molecular weight (M-w) and DB against molecular weight (M-w) are constructed. For the first time, it is found that there is a critical molecular weight (the value calculated is between 3200-3500 for the chosen real system) below, which DB is dependent on molecular weight and above which it becomes independent. A new term T+D/L, which has a maximum value of 20 and minimum of 1, characterizing all AB(2)-type hyperbranched polymers in general, has been introduced.

• 出版日期2006-9