Ladder polymers and improved methods of making the same

A polymer comprising at least one unit of Formula I, wherein Formula I consists of a subunit of Formula I′ and a subunit of Formula I″:

• wherein:
• each R1 represents a connection point to the polymer;
• each of the two R1 groups on the subunit of Formula I′ is on an adjacent carbon to another R1 group;
• each R2 represents a connection point between the subunit of Formula I′ and a carbon marked with an * on the subunit of Formula I″;
• each of the two R2 groups is on an adjacent carbon to another R2 group;
• X is, independently at each occurrence, selected from NRA, O, S, CRBRC, S═O, and C═O;
• when present, Y is, independently at each occurrence, selected from NRA, O, S, CRBRC, and C═O;
• wherein, when Y is present, at least one of X and Y is CRBRC or C═O;
• RA is, independently at each occurrence, selected from H, alkyl, —O-alkyl, or haloalkyl;
• RB and RC are, independently at each occurrence, selected from H, OH, SH, halo, amine, alkyl, —(H)C═O, —O-alkyl, and haloalkyl;
• or RB and RC, together with the atom to which they are attached, form a cycloalkyl, cycloalkenyl, heterocycloalkenyl, or heterocycloalkyl, which is optionally substituted with one or more RG, wherein RG is selected from H, alkyl, alkyoxyl, and hydroxyl;
• n is O or 1;
• and
• --- represents an optional bond.