A B-side mixture for the formulation of microcellular foam compositions or for the formulation of elastomer compositions, the mixture comprising an aliphatic polycarbonate polyol having a primary repeating unit with a structure: where R 1, R 2, R 3, and R 4 are, at each occurrence in the polymer chain, independently selected from the group consisting of -H, fluorine, an optionally substituted C 1-40 aliphatic group, an optionally substituted C 1-20 heteroaliphatic group, and an optionally substituted aryl group, where any two or more of R 1, R 2, R 3, and R 4 may optionally be taken together with intervening atoms to form one or more optionally substituted rings optionally containing one or more heteroatoms, wherein the mixture further comprises one or more additional polyols selected from the group consisting of polyether polyols, polyester polyols, and mixtures of these, wherein the aliphatic polycarbonate polyol is characterized in that, on average in the composition, the percentage of carbonate linkages is 85% or greater, wherein the aliphatic polycarbonate polyol has a structure P1: wherein, R 1, R 2, R 3, and R 4 are, at each occurrence in the polymer chain, independently selected from the group consisting of -H, fluorine, an optionally substituted C 1-30 aliphatic group, and an optionally substituted C 1-20 heteroaliphatic group, and an optionally substituted C 6-10 aryl group, where any two or more of R 1, R 2, R 3, and R 4 may optionally be taken together with intervening atoms to form one or more optionally substituted rings optionally containing one or more heteroatoms; Y is, at each occurrence, independently -H or the site of attachment to any of the chain-extending moieties described in the classes and subclasses herein; n is at each occurrence, independently an integer from 3 to 1,000; is a multivalent moiety; and x and y are each independently an integer from 0 to 6, where the sum of x and y is between 2 and 6, wherein is derived from a polyfunctional chain transfer agent having two or more sites from which epoxide/CO 2 copolymerization can occur. where R 1, R 2, R 3, and R 4 are, at each occurrence in the polymer chain, independently selected from the group consisting of -H, fluorine, an optionally substituted C 1-40 aliphatic group, an optionally substituted C 1-20 heteroaliphatic group, and an optionally substituted aryl group, where any two or more of R 1, R 2, R 3, and R 4 may optionally be taken together with intervening atoms to form one or more optionally substituted rings optionally containing one or more heteroatoms, wherein the mixture further comprises one or more additional polyols selected from the group consisting of polyether polyols, polyester polyols, and mixtures of these, wherein the aliphatic polycarbonate polyol is characterized in that, on average in the composition, the percentage of carbonate linkages is 85% or greater, wherein the aliphatic polycarbonate polyol has a structure P1: wherein, R 1, R 2, R 3, and R 4 are, at each occurrence in the polymer chain, independently selected from the group consisting of -H, fluorine, an optionally substituted C 1-30 aliphatic group, and an optionally substituted C 1-20 heteroaliphatic group, and an optionally substituted C 6-10 aryl group, where any two or more of R 1, R 2, R 3, and R 4 may optionally be taken together with intervening atoms to form one or more optionally substituted rings optionally containing one or more heteroatoms; Y is, at each occurrence, independently -H or the site of attachment to any of the chain-extending moieties described in the classes and subclasses herein; n is at each occurrence, independently an integer from 3 to 1,000; is a multivalent moiety; and x and y are each independently an integer from 0 to 6, where the sum of x and y is between 2 and 6, wherein is derived from a polyfunctional chain transfer agent having two or more sites from which epoxide/CO 2 copolymerization can occur.