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由于构成有机化合物分子的各原子或基团在空間分布的不同,在有机化合物中存在着多种异构現象。在这里,我們仅討論与高分子立体結构有关的几个問題。α-烯烃单体,CH_2=CHR,可能以CH_2=基团或以CHR=基团与高分子增长鏈末端相反应。如果所有单体分子均按一种方式与高分子增长鏈末端反应,則得到头一尾結构的聚合物: ～CH_2CHRCH_2CHRCH_2CHRCH_2CHR～高分子中也常含有一些結构为头-头或尾-尾的鏈段: ～CH_2CHRCHRCH_2CH_2CHRCHRCH_2～显然,头-头或尾-尾鏈段是两种加聚方式同时进行的結果。由于取代基R的共軛效应、超共軛效应及靜电誘导效应,无論在阳离子聚合,阴离子聚合或自由基聚合中,总有一种高分子鏈活性末端的能量比較低,生成此
Due to the different spatial distribution of atoms or groups of molecules that make up an organic compound, there are many isomeric phenomena in organic compounds. Here, we only discuss a few issues related to the three-dimensional polymer structure. α-olefin monomer, CH_2 = CHR, may CH_2 = group or with CHR = group and polymer chain terminal extension of the reaction. If all monomeric molecules react with the end of the macromolecule chain in one way, a polymer with a first-tailed structure is obtained: ~CH2CHRCH2CHRCH2CHRCH2CHR ~ Macromolecules often also contain segments of head- or tail-end structures : ~ CH_2CHRCHRCH_2CH_2CHRCHRCH_2 ~ Obviously, the head-tail or tail-tail segment is the result of two polyadditions simultaneously. Due to the conjugate effect of the substituent R, the hyperconjugation effect and the electrostatic induction effect, there is always a lower energy at the active end of the polymer chain in the cationic polymerization, the anionic polymerization or the radical polymerization to generate