Synthesis, Characterization, and Gas Permeation Properties

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Dendronization of Ethyl Cellulose
Figure 4. TGA curves of polymers 1, 2a–c, and 3a–c (in air, heating rate 10 ºC
min -1 ).
thermal stability. The retained thermal stability, despite the substitution of small
Figure 4. TGA curves of polymers 1, 2a–c, and 3a–c (in air, heating rate 10 ºC
hydroxy min groups by the bulky dendritic moieties, is most likely to arise from the
-1 ).
polarity of the dendritic substituents and the conjunctional ester linkage. The
incorporated dendritic structures are also capable of hydrogen bond formation as the
parent polymeric material (1) is; but it is probably the retainment of the individual
bond strengths in the polymer structure which is responsible for the retained thermal
stability upon dendron functionalization.
The glass transition temperature (Tg) of polymers 1, 2a–c, and 3a–c were
determined by the differential scanning calorimetric (DSC) analysis under nitrogen
(Figure 5). It was observed that the glass transition temperature (Tg) of 1 (132 ºC)
underwent a significant decrease as a result of the substitution by dendritic
appendages; for instance, the Tg of 2a–c and 3a–c were 53–69 ºC and 28–52 ºC,
respectively (Table 3). The variation in the glass transition temperature of the
dendritic macromolecules is dramatically affected by the nature of chain ends and the