Synthesis, chain conformation and crystal structure of poly(norbornadiene) having repeating 3,5-enchained nortricyclene units†,Polymer Chemistry

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Synthesis, chain conformation and crystal structure of poly(norbornadiene) having repeating 3,5-enchained nortricyclene units†
Polymer Chemistry ( IF 4.1 ) Pub Date : 2019-07-30 00:00:00 , DOI: 10.1039/c9py00757a
Claudio De Rosa _{1,

2,

3,

4} , Anna Malafronte _{1,

2,

3,

4} , Finizia Auriemma _{1,

2,

3,

4} , Miriam Scoti _{1,

2,

3,

4} , Rocco Di Girolamo _{1,

2,

3,

4} , Massimo Christian D'Alterio _{1,

2,

3,

4} , Giovanni Ricci _{4,

5,

6} , Giorgia Zanchin _{4,

5,

6} , Giuseppe Leone _{4,

5,

6}

Affiliation

The synthesis of a poly(3,5-tricyclo[2.2.1.0^2,6]heptylene) [poly(norbornadiene) (PNBD)] mediated by the TiCl₄/Et₂AlCl catalytic system is reported. This polymer is characterized by a rigid nortricyclene repeating structure and unique 3,5-enchainment and is obtained through a transannular cationic polymerization of norbornadiene involving both double bonds. The new PNBD is crystalline with high glass transition and melting temperatures due to the rigid tricyclic repeating structure. ¹³C NMR spectra indicate that the chains of PNBD contain only exo/exo (xx) and exo/endo (xn) nortricyclene repeating monomeric units. Models of the chain conformation and crystal structure of PNBD are also reported. Models of low conformational energy of isotactic and syndiotactic chains of PNBD have been obtained from the regular enchainment of xx and xn units. The model of the isotactic (xx)_m chain with s(2/1) helical symmetry assumes a nearly trans-planar conformation, whereas the models of the syndiotactic (xn–xn)_m and (nx–xn)_m chains with tc and ti symmetries, respectively, assume the conformations (TG⁻G⁻TG⁺G⁺)_n and (G⁻TTTG⁺T)_n, respectively. Ideal limit ordered models of the crystal structure have been obtained from the X-ray powder diffraction data and the conformational energy analysis. A good agreement between experimental and calculated powder diffraction profiles has been obtained for a limit ordered model of packing of syndiotactic chains (nx–xn)_m of PNBD with ti symmetry in an orthorhombic unit cell with axes a = 6.6 Å, b = 11.0 Å, and c = 6.84 Å according to the monoclinic space group P2₁/c. The real crystal structure of PNBD is disordered because of the possible presence of configurational disorder in the chains due to possible random enchainment of nortricyclene monomeric units in the xx, xn and nx configurations that produces conformational and packing disorder.

中文翻译：

具有重复3,5-链的降三环烯单元的聚（降冰片二烯）的合成，链构象和晶体结构†

报道了由TiCl ₄ / Et ₂ AlCl催化系统介导的聚（3,5-三环[2.2.1.0 ^2,6 ]庚烯）[聚（降冰片二烯）（PNBD）]的合成。该聚合物的特征在于具有刚性的降三环烯重复结构和独特的3,5-链，并且是通过降冰片二烯的跨环阳离子聚合反应（包括两个双键）获得的。新型PNBD由于具有刚性的三环重复结构，具有高玻璃化转变温度和熔融温度的晶体。¹³ C NMR光谱表明PNBD的链仅包含exo / exo（xx）和exo / end（xn）。）降三环素重复单体单元。还报道了PNBD的链构象和晶体结构模型。PNBD的等规和间规链的低构象能量模型是从xx和xn单元的常规链中获得的。具有s（2/1）螺旋对称性的等规（xx）_m链模型假定近似反平面构象，而具有t c的间同（xn–xn）_m和（nx–xn）_m链模型和Ť我对称性，分别承担的构象（TG ^-G ^- TG ⁺ G ⁺）_n和（G ^- TTTG ⁺ T）_n。从X射线粉末衍射数据和构象能量分析获得了晶体结构的理想极限有序模型。已经为限制获得的实验和计算的粉末衍射曲线之间的良好的一致性有序间同立构链（的填料的模型NX-xn）映射_米与PNBD的吨我在与轴的正交晶胞对称性一个= 6.6埃，b = 11.0 Å，根据单斜空间群，c = 6.84ÅP 2 ₁ / c。PNBD的真实晶体结构是无序的，因为由于xx，xn和nx构型的降三环烯单体单元可能发生随机链结而导致构象和堆积无序，因此链中可能存在构型无序。

更新日期：2019-07-30

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