Another for preparing TPDB uses rare earth-based catalysts, such as acid organic salts of the lanthanide series (e.g., versate of di-dymium: a mixture composed of 72% Nd, 20% La, and 8% Pr) (23), (25).
Anionic systems with potassium-based complexes are able to produce TPDB with 90-95% of 1,4-trans units and with acceptable activity, yet they do not hold a "living" character (21), (22), and the polymer is a heterogeneous mixture because there is always a number of in-soluble TPDB (21), (22).
Therefore, it was considered timely to study the synthesis of TPDB via anionic polymerization and their characterization to gather information to determine the effect of the number of 1,4-trans units on the properties of this kind of polymer.
The synthesis of TPDB was pursued by examining the polymerization of 1,3-butadiene using cyclohexane solutions of trioctyl aluminum [Al[([C.sub.8][H.sub.17]).sub.3]], n-butyl lithium (n-([C.sub.4] [H.sub.9])Li), and barium 2-ethyI-hexoxide [(RO).sub.2] Ba.
The diffraction pattern of the PBDN displays only the amorphous halo, while those of the TPDB exhibit two main diffraction peaks: one intense at 22.47[degrees] and other weak at 30.60[degrees], which have been related to the crystalline reflections (200) and (220), respectively (41), (49), along with an amorphous halo at 20.80[degrees], which belongs to their noncrystalline part.
Smooth curves were fitted to the relationships between the measured plant data, total plant dry biomass (TPDB), leafblade dry biomass (LDB), and LAI; and time (t).
Estimated coefficients and their standard errors for TPDB, LDB, SDB, and LAI are presented in Tables 1 and 2.
With the noted exception of the 76 vs 114 cm contrast at sample number 11 (R7), the estimated TPDB of soybean grown in either the 38- or 76-cm row width was significantly greater than that of soybean in the 114-cm row width at all sample times (Fig.
The TPDB of soybean growing in the 38-cm row width was significantly larger than that of soybean growing in the 76-cm row width until sample week 5 (R3), after which the two treatments were similar.