Polyol block copolymer, compositions and processes therefor

A polyol block copolymer comprising a polycarbonate block, A, (A′-Z′—Z—(Z′-A′) n-), and polyethercarbonate blocks, B, wherein the polyol block copolymer has the polyblock structure:

• B-A′-Z′—Z—(Z′-A′-B)n
• wherein n=t−1 and wherein t=the number of terminal OH group residues on the block A;
• wherein each A′ is independently a polycarbonate chain having at least 70% carbonate linkages, and wherein each B is independently a polyethercarbonate chain having 50-99% ether linkages and at least 1% carbonate linkages;
• wherein Z′—Z—(Z′) n is a starter residue;
• wherein Z is selected from optionally substituted alkylene, alkenylene, alkynylene, heteroalkylene, heteroalkenylene, heteroalkynylene, cycloalkylene, cycloalkenylene, heterocycloalkylene, heterocycloalkenylene, arylene, heteroarylene, an alkylarylene, heteroalkylarylene, heteroalkylheteroarylene or alkylheteroarylene group, or Z may be a combination of any of these groups;
• wherein Z′ is selected from —O—, —NR′—, —S—, —C(O)O—, —P(O) (OR′)O—, —PR′ (O) (O—)2 or —PR′ (O)O—;
• wherein R′ is selected from H, or optionally substituted alkyl, heteroalkyl, aryl, heteroaryl, cycloalkyl or heterocycloalkyl;
• and
• wherein the polycarbonate block A is prepared using an epoxide.