Structure and origin of long-chain branching and gel in natural rubber
Structure and origin of long-chain branching and gel in natural rubber
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发表时间：
2005
影响因子：
0.4
通讯作者：
L. Tarachiwin;Yasuyuki Tanaka;J. Sakdapipanich
中科院分区：
文献类型：
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作者：
L. Tarachiwin;Yasuyuki Tanaka;J. Sakdapipanich
NMR研究揭示了天然橡胶（NR）的基本结构，包括引发端基（ω-末端）、两个反式-1，4异戊二烯单元、一长串顺式-1，4异戊二烯单元和链端基（α-末端）。已经假定功能性ω-和α-末端基团分别通过与蛋白质和磷脂缔合形成分支点。用蛋白水解酶处理天然胶乳，使含有蛋白质的分支点分解成分支分子，其中残余的分支点可通过与甲醇钠在甲苯溶液中的酯交换反应分解成线性分子。α-末端的分支点被认为是由连接到橡胶链的磷酸或二磷酸末端基团的磷脂产生的。脂肪酶、磷脂酶A 2、B、C和D以及磷酸酶对NR中磷脂的选择性分解为磷脂形成长支链提供了确凿的证据。
NMR studies have revealed the fundamental structure of natural rubber (NR) composed of the initiating terminal (ω-terminal), two trans-1,4 isoprene units, a long sequence of cis-1,4 isoprene units and the chain-end group (a-terminal). The functional ω- and α-terminal groups have been postulated to form branch-points by association with proteins and phospholipids, respectively. The treatment of NR latex with a proteolytic enzyme decomposes the branch-points containing proteins to form branched molecules, the residual branch-points in which can be decomposed by transesterification with sodium methoxide in toluene solution to form linear molecules. The branch-points at the α-terminal were postulated to be originated by phospholipids which linked to the phosphate or diphosphate terminal group of rubber chain. The selective decomposition of phospholipids in NR by treatment of lipase, phospholipases A 2 , B, C and D, and phosphatase provided conclusive evidence on the formation of long-chain branchings composed of phospholipids.