(Novc mbcr 15, 1963) F our distinct polym.crs wc rc isolated fr om t he p olym eri zat ions of accnaph Lh.v lcnc ill it iated by boron t rifiu oride a nd n-butyllithium. A syn d iotactic or isotactic co nform atio n was assigned to t h ese prod ucts on t he basis of infrared a nd N M R evidence. T he conformat ions and reaction details a re di sc ussed. I . IntroductionA survey of the fi eld of ster eor egulm' polym ers indicated th at little h as been don e in delib er at e control of chain conformation by mea ns of steric hindmn ce of bulky groups [1] .1.2 In t his sense, acenap hLl1 ylene as a vin yl mon om er Wt1S parli culnrly int eresLin g du e Lo the extreme bulk fi nd rigidit y of the 1 ,8 -pel"in~tph t h yle n e residue. Addition al feftt ures wer e its slm in ed five -mem bered ring [b ] and well defin ed co nditi ons for polYllleri zfl tio li.Th e polymers of ftcenflpil thylene h ftve been exte nsively investi gated. D ziewonski and his coworke rs [2] we re able to show iO llic, therm ftl, ftll d solicl-st~l te polymerizat ion of ace lHlphlhylene before t he prese nt-day tools for m easuring Jl igh molecular weights were available. Their investigl1tio ns started in 1912 rmel ended in ] 924. Since then, oL her work· ers have examin ed these polymers. Jones '.:vote adclecl ill proof: The paper by G. Nalla, G . Dall' Asta, G. M azzanti, ancl G . Metroni (Mukro11l01. Cilelll. 69 , 124, 1963) describes the polymerization of cyclobutcnc with Ziegler cMa lysts. The ste reochemistry of t hc products arc ap parently identical with the case described hero. Instead of cis or trans, the nomenclature tILTeo or eTl/tltro, rrs pcctivl'iy, is used. 165th e plftl1e of t.he papcr a,nd tll e B 's are ill fl p ara llel plan e b elow, was self-termin ati ng . Ri ll g Jormat.ion was fftvo red . I n fact, both a cyclic trimer and tetranw r ftre kn own [2}. The cis-sy ndiolactic p olymer II was impossible to con str uct beyond th e Lrimer. IIT he Silme nolation is used here ,1S for J ~lbove.The A's werc acLuftlly Lwisled out of plane due Lo storic hindrance. trans-Iso tactic poJ~-acenaphLhy lene, lIT , for med a helix. 3 III 3 'r'he limited rotation about the back bone carbon-carbon bonds due to stcric hind rance of the 1,8-acenaphthylcnc residues suggests that change in the se nse of the helix of III is not possible if a penultimate effect in fl uences the course of add ition. Of course, a mixture of d a nd 1 cha ins would be produced, unless a n assynlctric initiator wcro used.