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Acetamide(C2), propionamide(C3), butyramide(C4), isobutyramide(i-C4), isovaleramide(i-C5) and trimethylacetamide(t-C5) groups each were introduced to the terminals of hyperbranched polyethylenimine(HPEI) through the amidation reaction between HPEI and the corresponding anhydride. Moreover, HPEIs terminated with two kinds of amides were also prepared. The first amide was fixed to be i-C4 with 52% degree of amidation(DA), and the second amide varied from C2, C3, C4, i-C5 to t-C5. All the polymers were characterized by 1H-NMR. Turbidimetry measurements were performed for these polymers in water at different temperatures. With respect to the polymers bearing only one kind of amide group, except C2, all the other amide groups could render thermoresponsive properties to HPEI. The specific ordering of these amide groups to reduce the cloud point temperature(Tcp) was as follows: i-C5 > t-C5 > C4 > i-C4 > C3. Moreover, the more branched i-C4 and t-C5 were better groups than their less branched isomers C4 and i-C5 in the Tcp range of 12-51 °C to render the sharper phase transition to the thermoresponsive polymers. As for the polymers bearing two kinds of amide groups, the further introduction of C2, C3, C4, i-C5 or t-C5 could effectively endow HPEI bearing 52% of i-C4 with thermoresponsive properties. The specific ordering of these second amide groups to reduce the Tcp was as follows: i-C5 > C4 > i-C4 > C3 > C2. C4, i-C5 and t-C5 were all effective second amide groups to prepare the thermoresponsive polymers with sharper phase transition.
Acetamide (C2), propionamide (C3), butyramide (C4), isobutyramide (i- C4), isovaleramide (i- C5) and trimethylacetamide (t- C5) groups each were introduced to the terminals of hyperbranched polyethylenimine amidation reaction between HPEI and the corresponding anhydride. HPEIs terminated with two kinds of amides were also prepared. The first amide was fixed to be i-C4 with 52% degree of amidation (DA), and the second amide varied from C2, C3, C4, i-C5 to t-C5. All the polymers were characterized by 1H-NMR. Turbidimetry measurements were performed for these polymers in water at different temperatures. With respect to the polymers bearing only one kind of amide group, except C2 All the other amide groups to render the thermoresponsive properties to HPEI. The specific ordering of these amide groups to reduce the cloud point temperature (Tcp) was as follows: i-C5> t-C5> C4> i-C4> C3. , the more branched i-C4 and t-C5 were better groups than their less branched isomers C4 and i-C5 in the Tcp range of 12-51 ° C to render the sharper phase transition to the thermoresponsive polymers. As for the polymers bearing two kinds of amide groups, the further introduction of C2, C3, C4, i- C5 or t-C5 could effectively endow HPEI bearing 52% of i-C4 with thermoresponsive properties. The specific ordering of these second amide groups to reduce the Tcp was as follows: i-C5> C4> i-C4> C3> C2. C4, i-C5 and t-C5 were all effective second amide groups to prepare the thermoresponsive polymers with sharper phase transition.