▁know ▁natural ▁rub ber ▁when ▁we ▁see ▁it !" ▁ ▁Fra ction ation ▁of ▁the ▁sample ▁then ▁showed ▁a ▁mixture ▁of ▁c is - 1 , 4 - poly is op rene ▁and ▁poly eth yl ene . ▁The ▁fact ▁that ▁is op rene ▁had ▁polym er ized ▁was ▁not ▁unexpected , ▁but ▁the ▁high ▁degree ▁of ▁s tere o ▁control ▁was ▁unexpected . ▁They ▁immediately ▁recognized ▁the ▁importance ▁of ▁this ▁discovery ▁and ▁began ▁an ▁inten se ▁program ▁to ▁el uc id ate ▁the ▁chem istry ▁and ▁variables ▁associated ▁with ▁di ene ▁polym er izations . ▁ ▁The ▁successful ▁dup lication ▁of ▁natural ▁rub ber ▁was ▁a ▁goal ▁that ▁had ▁been ▁sought ▁by ▁many ▁scient ists ▁for ▁nearly ▁one ▁hundred ▁years . ▁An ▁extensive ▁synth etic ▁rub ber ▁program ▁was ▁carried ▁out ▁during ▁World ▁War ▁II , ▁one ▁of ▁the ▁object ives ▁being ▁to ▁accomplish ▁this ▁synth esis . ▁The ▁supply ▁of ▁natural ▁rub ber ▁was ▁limited ▁for ▁the ▁military ▁during ▁World ▁War ▁II , ▁because ▁natural ▁rub ber ▁plant ations ▁were ▁not ▁available ▁to ▁the ▁al lied ▁forces ▁due ▁to ▁the ▁Japanese ▁occupation ▁of ▁many ▁of ▁the ▁world ' s ▁rub ber ▁plant ations . ▁ ▁With ▁the ▁process ▁well ▁defined , ▁the ▁scale - up ▁of ▁the ▁process ▁from ▁ 5 0 - gram ▁labor atory ▁batch es ▁to ▁ton - size ▁production ▁was ▁started . ▁In ▁less ▁than ▁six ▁months , ▁they ▁scale d ▁the ▁process ▁to ▁production - size ▁quantities , ▁made ▁bus ▁and ▁tr uck ▁t ires ,