The thiol–ene click reaction was applied to modify poly(isobutylene-co-isoprene) (IIR) by two different strategies using carboxylated thiols (mercaptanoic acids) with different alkyl spacer chain lengths. In the first approach, the direct radical-promoted addition of thiols across the 1,4-isoprene units proceeded with 80–90% conversion of the internal double bonds. An alternate method involving the conversion of sterically hindered 1,4-isoprene units to pendant double bonds through epoxidation and hydrolysis prior to the click reaction proceeded with 90–98% conversion of the alkene moieties. The carboxylated IIR derivatives were characterized by 1H NMR, FT-IR spectroscopy, and gel permeation chromatography analysis. Irrespective of the synthetic strategy used, the yields of the reactions decreased as the length of the alkyl spacer in the mercaptanoic acid increased. The outcomes of the reactions also depended on the amounts of solvent and free radical initiator used. Carboxylated butyl rubber derivatives were obtained by reacting the isoprene units in the isobutylene copolymer with alkylmercaptanoic acids comprising alkyl spacers of different lengths. The yield of the reactions varied from 80 to 90% for direct reaction of the copolymer containing 1,4-isoprene units, but increased to 90–98% if the 1,4-units were isomerized to terminal alkenes prior to the reactions.

中文翻译：

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通过硫醇-烯点击化学轻松合成聚（异丁烯-共-异戊二烯）（IIR）羧化衍生物

通过两种不同的策略，使用具有不同烷基间隔链长度的羧化硫醇（硫醇酸），将硫醇-烯点击反应用于改性聚（异丁烯-共-异戊二烯）（IIR）。在第一种方法中，直接自由基促进硫醇在 1,4-异戊二烯单元上的添加进行了 80-90% 的内部双键转化。另一种方法是在点击反应之前通过环氧化和水解将位阻 1,4-异戊二烯单元转化为侧链双键，烯烃部分转化率为 90-98%。通过 1 H NMR、FT-IR 光谱和凝胶渗透色谱分析表征了羧化 IIR 衍生物。无论使用何种合成策略，随着硫醇酸中烷基间隔基的长度增加，反应的产率降低。反应的结果还取决于溶剂和自由基引发剂的用量。通过使异丁烯共聚物中的异戊二烯单元与包含不同长度的烷基间隔基的烷基硫醇酸反应获得羧化丁基橡胶衍生物。对于含有 1,4-异戊二烯单元的共聚物的直接反应，反应的产率从 80% 到 90% 不等，但如果 1,4- 单元在反应前异构化为末端烯烃，则反应产率会增加到 90-98%。通过使异丁烯共聚物中的异戊二烯单元与包含不同长度的烷基间隔基的烷基硫醇酸反应获得羧化丁基橡胶衍生物。对于含有 1,4-异戊二烯单元的共聚物的直接反应，反应的产率从 80% 到 90% 不等，但如果 1,4- 单元在反应前异构化为末端烯烃，则反应产率会增加到 90-98%。通过使异丁烯共聚物中的异戊二烯单元与包含不同长度的烷基间隔基的烷基硫醇酸反应获得羧化丁基橡胶衍生物。对于含有 1,4-异戊二烯单元的共聚物的直接反应，反应的产率从 80% 到 90% 不等，但如果 1,4- 单元在反应前异构化为末端烯烃，则反应产率会增加到 90-98%。