A series of shape-memorized crosslinked ester-type polyurethanes (PUs), based on different compositions of 4,4Ј-diphenyl methane diisocyanate (MDI), poly(butylene adipate) glycol (PBAG) with different molecular weight (MW) and trimethylol propane (TMP), were synthesized. The morphology of samples was investigated by using DSC, WAXD, and dynamic mechanical analysis (DMA). It was found that the morphology of the soft segment, which was PBAG with a different MW, was in an amorphous state and no crystalline domain was found. By increasing the crosslinked density (varying the content of TMP) or decreasing the length of the soft segment (MW of PBAG), the glass transition temperature of studied samples increased. But the range of transition broadened and the modulus ratio EЈ (T g Ϫ20°C) /EЈ (T g ϩ20°C) also decreased. The shape-memory behavior was studied by the bending test method adopted from the shape-memory alloy. The sample with high T g showed not only a high recovered temperature (T r ) but also a high recovered rate (V r ) with a high modulus ratio. By introducing the chemical crosslinked structure, the deformed samples completely recovered their original shape and rendered shape-memory behavior under the complex deformation. The shape-memorized crosslinked ester-type PUs can be applied at different operating temperatures. A mechanical viscoelastic model is discussed for the shape-memory behavior of PUs, and the modified Bonart's viscoelastic model properly describes the mechanism of the shape memory of PUs.

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SynopsisNovel aromatic polyamides, polyimides, and polyureas containing 1,3,5-triazine rings were prepared by the reaction of 2-anilino-4-aminoanilino-6-aminophenyl-l,3,5-triazines with aromatic dicarboxylic acid chlorides, pyromellitic dianhydride, and diisocyanates, respectively. All polymers were soluble in polar aprotic solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and pyridine. The glass transition temperatures of polymers were in the range of 220-260OC. The thermal stabilities of polymers were evaluated by thermogravimetric analysis in air. These polymers were stable up to 420°C for polyamides, 47OOC for polyimides, and 3OOOC for polyureas.

SynopsisA series of new aromatic polyamides, polyimides, and polyureas containing 1,3,5-triazine rings in the main chain and two flexible long side chains for each unit, were prepared by the reaction of 2-( N-phenyl-N-octadecylamino ) -4-( N-aminophenyl-N-octadecylamino) -6-aminophenyl-1,3,5-triazines with aromatic diacid chlorides, pyromellitic dianhydride, and diisocyanates, respectively. These polymers were soluble in tetrahydrofuran, chloroform, and benzene, but had poor solubility in polar aprotic solvents such as dimethyl sulfoxide and N,N-dimethylformamide. These polymers were stable up to 410°C for polyamides, 430°C for polyimides, and 290°C for polyureas in air. The differential scanning calorimetric studies of the polymers indicated that the degree of side-chain crystallinity based side chain was 6-10%.

ABSTRACT:Novel comb-like poly(amide-guanamine)s, poly(urea-guanamine)s and poly-(imide-guanamine)s which contain three long alkyl side-chains in each repeating unit (three sidechains polymers), were synthesized by the reaction of 2,4-bis(amino-N-octadecylanilino)-6-heptadecyl-l,3,5-triazines with aromatic or aliphatic diacid chlorides, diisocyanates and pyromellitic dianhydride, respectively. Making reference to the three side-chain polymers, the corresponding one side-chain polymers were also prepared using 2,4-bis(aminoanilino)-6-heptadecyl-1,3,5-triazine as a monomer. Although the one side-chain polymers were insoluble in tetrahydrofuran, chloroform, toluene and benzene, the three side-chains polymers except polyimides were readily soluble in these solvents. These polymers had good thermal stability though the bulky long alkyl groups were present. The three side-chains polymers are characterized by side-chain crystallinity. The one side-chain polymers were found to show low crystallinity by differential scanning calorimetry and wide angle X-ray diffraction. The influence of the main-chain structure on the sidechain crystallization was investigated.KEY WORDS Comb-Like Polymer/ 1,3,5-Triazine / Long Alkyl Group/ Poly(amide-guanamine) / Poly(urea-guanamine) / Poly(imide-guanamine) / Side-Chain Crystallization / Comb-like polymers containing rigid mainchain and flexible long alkyl side-chains have attracted great interest because this specific combination is expected to lead to a favorable property. 1 -5 For example, N-octadecylated poly(p-phenylene terephthalamide) containing the rigid backbone and flexible alkyl sidechains shows side-chain crystallization and liquid crystalline behavior of the lyotropic type. For dynamic mechanical properties, two characteristic relaxations were observed, and assigned to the crystalline and amorphous phase of the side-chains, respectively. 3 In previous papers of this series 6 -9 we investigated the properties of several aromatic comb-like polymers prepared from diamines containing 1,3,5-triazine ring with one (1 6 ) or two long alkyl groups (II, 7 111 8 and IV 9 ). II 92Polym.