Influence Of Aliphatic-amide Terminals On The Thermoresponsive Properties Of Modified Hyperbranched Polyethylenimines

In this dissertation, water-soluble hyperbranched polyethylenimine (HPEI) possessing a large amount of amino groups was endowed thermoresponsive properties in water through the introduction of aliphatic amide groups. The details were as follows:1. Acetamide (C2), propionamide (C3), butyramide (C4), isobutyramide (i-C4), isovaleramide (/-C5) and trimethylacetamide (i-C5) groups were each introduced to the terminals of HPEI through the amidation reaction between HPEI and the corresponding anhydride. All the polymers were characterized well by1H NMR, from which their structures were verified and the degree of amidation (DA) data were obtained. Turbidimetry measurement was performed for these polymers in water at different temperature. With respect to the polymers bearing only one kind of amide group, except of C2, all the other amide groups could render thermoresponsive property to HPEI. The specific ordering of these amide groups to reduce the cloud point temperature (Tcp) was as follows:/-C5>t-C5>C4>/-C4> C3. Moreover, the more branched i-C4and t-C5were better groups than their less branched isomer C4and i-C5to render the sharper phase transition to the thermoresponsive polymers.2. HPEIs terminated with two kinds of amides were also prepared. The first amide was fixed to be i-C4with a DA of52%, and the second amide varied from C2,C3, C4, i-C5to t-C5. All the polymers were characterized well by1H NMR, from which their structures were verified and the DA data were obtained. The specific ordering of these second amide groups to reduce the Tcp was as follows:i-C5>C4> i-C4> C3>C2.C4,i-C5and t-C5were all effective second amide groups to prepare the thermoresponsive polymers with sharper phase transition.3. The influence of spatial distribution of i-C4and C2groups on the thermoresponsive properities of HPEI was studied. Three kinds of modified HPEIs were prepared. The first kind of modified HPEIs are named as WD whose character is that iC4groups are located at the outer section of HPEI skeleton, while C2groups are located in the inner part of HPEI skeleton. The second kind of modified HPEIs are named as ND whose character is that C2groups are located at the outer section of HPEI skeleton, while i-C4groups are located in the inner part of HPEI skeleton. The third kind of modified HPEIs are named as WG whose character is that i-C4and C2 groups are located at both the outer and inner sections of HPEI skeleton. When the DA values of i-C4and C2are the same, the Tcp values of these polymers were in the ordering of WG>ND>WD. Moreover, they have the similar phase transition sharpness.