De‐yue Yan

Controlled/“living” radical polymerization of styrene catalyzed by FeCl2/succinic acid

A new ligand, succinic acid, was successfully used for atom transfer radical polymerization. The reaction was carried out at 40 to 100°C in bulk with α-bromoethyl benzene as the initiator and FeCl 2 /(succinic acid) as the catalyst system. The molecular weight of the resulting polymer increases with increasing monomer conversion, however, it is somewhat lower thant the theoretical value. The polydispersity index is relatively low (M w /M n = 1,30) even though there may be a possible chain transfer reaction during the polymerization. The enthaly of the equilibrium between active species and dormant ones was calculated to be 2.15 kcal. mol.

Hyperbranched Polymers Made from A2- and BB′2 -Type Monomers, 3. Polyaddition ofN-Methyl-1,3-propanediamine to Divinyl Sulfone

The new approach to the synthesis of hyperbranched polymers from commercially available A 2 - and BB 2 -type monomer has been developed further. In this work, hyperbranched poly(sulfone amine)s with multiple amino end groups were prepared by direct polyaddition of N-methyl-1,3-propanediamine (NPA, BB 2 ) to divinyl sulfone (DV, A 2 ). The polymerization mechanism is presented and demonstrated with FT-IR, HPLC, and MS. During the reaction, the secondary amino groups of NPA react with the vinyl groups of DV within 12 s, generating dimers that can be regarded as new AB 2 -type monomers. Further polymerization of the new monomers leads to hyperbranched poly(sulfone amine)s. The influence of the reaction conditions, such as the feed ratio and solvents, on the polymerization has been investigated. When the molar feed ratio of DV to NPA is equal to 1 (A/B/B = 2/1/2), no crosslinking is observed in water or organic solvents. When the feed ratio of DV to NPA is equal to 3/2 (A/B/B = 3/1/2), no gelation occurs in chloroform or other organic solvents, such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone. Interestingly, when the polymerization was carried out in water with a feed ratio of 3/2, the reaction mixture got turbid within 20-30 min and gelation occurred with 15-20 h.

In situ FTIR spectroscopy study on the melting process of isotactic poly(propylene)

The melting process of isotactic poly(propylene) (iPP) sample isothermally crystallized at 130°C for half an hour is carefully studied by means of variable-temperature FTIR spectroscopy and DSC. Based on the IR intensity changes of regularity and conformational bands vs. temperature, it is found that the helical structure of macromolecular chains can be retained in the iPP melt after the polymer crystals are melted. When temperature is somewhat higher than 170.5°C, the macromolecules get sufficient energy from surroundings to overcome the energy barrier of helical structure, so the quantity of helical structure in iPP melt reduces dramatically. This conclusion is also confirmed by DSC studies on crystallization behavior of different iPP melts. The activation energy to destroy the helical structure of iPP melt is 60.1 kcal/mol determined by the Snyder method. After the major transition, some level of order still persists in the melt and it is gradually lost at higher temperatures.

Influence of termination and transfer on molecular weight distribution of polymer—10. Chain transfer to monomer and impurity

Abstract The kinetics of ionic polymerization with instantaneous initiation, impurity transfer and chain transfer to monomer is studied by means of non-steady state procedure developed in previous publications. The expressions for molecular size distribution and other molecular parameters are derived rigorously. With the aid of the derived formulae, the molecular size distribution and the values of other molecular parameters for the resultant polymer can be calculated from the initial conditions of polymerization and reaction time.

Cationic Transannular Oligomerization Of 1,5-Cyclooctadiene

Cationic transannular oligomerization of 1,5-cyclooctadiene initiated by BF3OEt2 and AlCl3 is presented in this paper. The number-average molecular weight of the resultant polymer is about 1,500, and the softening temperature range is 140–160°C. By means of NMR, IR and PC-MS analyses, the chain structure of poly(l,5-cyclooctadiene) proposed earlier by Marvel et al. is corroborated.