Provided is a method of forming a film having a surface structure of a random wrinkles. A compound according to the present invention is coated and then, a film having a surface structure of random wrinkles may be simply formed through simple ultraviolet (UV) curing or thermosetting. When the film thus formed is used in an organic light emitting device, light generated from the organic light emitting device is scattered on surfaces of the random wrinkles to prevent light guide or total reflection, and thus, light is extracted to the outside. That is, a random structure disposed at the outside of the device performs a light extraction function and consequently, light efficiency of the organic light emitting device may be increased.

A method of preparing a branched polymer comprises the free radical polymerisation of a multivinyl monomer in the presence of a chain transfer agent, using a source of radicals, wherein the extent of propagation is controlled relative to the extent of chain transfer to prevent gelation of the polymer. The average length of each vinyl polymer chain within the product is short.

An anion exchange membrane obtainable by curing a curable composition comprising: (a) a monomer (a) of Formula (I) AR.sup.1(CH.sub.2).sub.nN.sup.+(R.sup.aR.sup.b)(CH.sub.2).sub.n-AR.sup.2, X.sup. wherein: each n independently has a value of 1 or 2; (i) R.sup.a and R.sup.b are each independently an optionally substituted C.sub.1-3-alkyl group or an optionally substituted C.sub.2-3-alkenyl group; or (ii) R.sup.a and R.sup.b, together with the positively charged nitrogen atom to which they are attached, form an optionally substituted 5- or 6-membered ring; or (iii) one of R.sup.a and R.sup.b is an optionally substituted C.sub.1-3-alkyl group or an optionally substituted C.sub.2-3-alkenyl group and the other of R.sup.a and R.sup.b, together with the group of formula AR.sup.1(CH.sub.2).sub.nN.sup.+, forms an optionally substituted 5- or 6-membered ring; or (iv) R.sup.a, together with the group of formula AR.sup.1(CH.sub.2).sub.nN.sup.+, forms an optionally substituted 5- or 6-membered ring, and R.sup.b, together with the group of formula N.sup.+(CH.sub.2).sub.n-AR.sup.2, forms an optionally substituted 5- or 6-membered ring; X is an anion; and AR.sup.1 and AR.sup.2 each independently comprise aromatic groups; wherein: (I) at least one of AR.sup.1 and AR.sup.2 comprises a curable ethylenically unsaturated group; (II) the monomer (a) of Formula (I) comprises at least two curable ethylenically unsaturated groups; and (III) the molar fraction of component (a) in relation to all curable components of the curable composition is at least 0.90.

An anion exchange membrane obtainable by curing a curable composition comprising: (a) a monomer (a) of Formula (I) AR.sup.1(CH.sub.2).sub.nN.sup.+(R.sup.aR.sup.b)(CH.sub.2).sub.n-AR.sup.2, X.sup. wherein: each n independently has a value of 1 or 2; (i) R.sup.a and R.sup.b are each independently an optionally substituted C.sub.1-3-alkyl group or an optionally substituted C.sub.2-3-alkenyl group; or (ii) R.sup.a and R.sup.b, together with the positively charged nitrogen atom to which they are attached, form an optionally substituted 5- or 6-membered ring; or (iii) one of R.sup.a and R.sup.b is an optionally substituted C.sub.1-3-alkyl group or an optionally substituted C.sub.2-3-alkenyl group and the other of R.sup.a and R.sup.b, together with the group of formula AR.sup.1(CH.sub.2).sub.nN.sup.+, forms an optionally substituted 5- or 6-membered ring; or (iv) R.sup.a, together with the group of formula AR.sup.1(CH.sub.2).sub.nN.sup.+, forms an optionally substituted 5- or 6-membered ring, and R.sup.b, together with the group of formula N.sup.+(CH.sub.2).sub.n-AR.sup.2, forms an optionally substituted 5- or 6-membered ring; X is an anion; and AR.sup.1 and AR.sup.2 each independently comprise aromatic groups; wherein: (I) at least one of AR.sup.1 and AR.sup.2 comprises a curable ethylenically unsaturated group; (II) the monomer (a) of Formula (I) comprises at least two curable ethylenically unsaturated groups; and (III) the molar fraction of component (a) in relation to all curable components of the curable composition is at least 0.90.