Poly(vinyl acetal) resin compositions, layers, and interlayers having enhanced properties

An interlayer comprising:

• a first resin layer comprising a first poly(vinyl acetal) resin and a first plasticizer;
• and
• a second resin layer adjacent to said first resin layer, wherein said second resin layer comprises a second poly(vinyl acetal) resin and a second plasticizer, wherein said second plasticizer is present in said second resin layer in an amount of at least 50 parts per hundred parts of resin (phr) and wherein the difference between the amount of said first plasticizer in said first resin layer and the amount of said second plasticizer in said second resin layer is more than 10 phr,
• wherein at least one of said first and said second poly(vinyl acetal) resins comprises at least 5 weight percent of residues of an aldehyde other than n-butyraldehyde, based on the total weight of aldehyde residues of said first or said second poly(vinyl acetal) resin, and
• wherein the glass transition temperature of said first resin layer is at least 3° C. higher than the glass transition temperature of said second resin layer, and wherein the absolute value of the difference between the refractive index of said first resin layer and the refractive index of said second resin layer is not more than 0.010;wherein the difference between the residual hydroxyl content of said first poly(vinyl acetal) resin and the residual hydroxyl content of said second poly(vinyl acetal) resin is at least 2 weight percent and wherein said interlayer has a haze value of less than 5 percent.