A method for forming a melt blend that is suitable for forming an article selected from the group consisting of siding, gutters, downspouts, pipe, pipe fittings, molding, fencing, decking, window frames, window profiles, bottles, jars, appliance housings, automotive body side molding, rigid film, and rigid sheet, comprising the steps of: forming a macromonomer aqueous emulsion by a process comprising emulsion polymerization of at least one first ethylenically unsaturated monomer in the presence of a transition metal chelate chain transfer agent, wherein said macromonomer comprises 20 to 100 wt%, based on the total weight of the macromonomer, of at least one α-methyl vinyl monomer, a vinyl monomer bearing no α-methyl group, or combinations thereof, provided that when a vinyl monomer bearing no α-methyl group is present, as polymerized units, in the macromonomer, the macromonomer must be terminated by a unit derived from an α-methyl vinyl monomer; forming an aqueous comb copolymer composition by a process comprising forming a polymerization reaction mixture by a process comprising combining said macromonomer aqueous emulsion with a monomer composition comprising at least one kind of ethylenically unsaturated monomer; polymerizing said polymerization reaction mixture in the presence of a free radical initiator; isolation of the comb copolymer as a powder from said aqueous comb copolymer composition; (a) forming a solids blend comprising polyvinyl chloride and said powder of said comb copolymer; and (b) mixing and heating said solids blend to form said melt blend; wherein said comb copolymer comprises at least two copolymer segments; wherein a first copolymer segment is a backbone and a second copolymer segment is a graft segment; wherein at least one copolymer segment of said comb copolymer is miscible with said polyvinyl chloride, wherein the polymeric backbone of the comb copolymer is linear and each graft segment of the comb copolymer is formed by a macromonomer that is grafted to the polymer backbone; wherein said macromonomer has degree of polymerization of 20 to 1,000wherein said melt blend has a melt processing improvement term (I MP) having a value of at least 10; wherein the I MP is calculated using the following equations: I MP = I FTI + I FTP + I ET; I FTI = ( FTI without PA - FTI with PA / FTI without PA x 100; I FTP = ( FTP without PA - FTP with PA / FTP without PA x 100; I ET = ET with PA / ET without PA - 1 x 100; where FTI represents the fusion time, which is the time interval in seconds, determined on a Haake Rheocord 90 melt flow instrument with a Haake Bowl attachment using counter rotating paddles with a speed of 60 rpm, between the initial loading of the test sample at 170°C and the torque maximum which occurs on fusion, FTP represents fusion temperature, which is the temperature in °C at which the solids blend becomes a melt blend in the melt flow instrument and is measured at the point at which the torque reaches its peak value, ET represents equilibrium torque, which is the torque value measured on the melt flow instrument once the torque has become constant after peak torque has occurred and PA represents the comb copolymer additive. forming a macromonomer aqueous emulsion by a process comprising emulsion polymerization of at least one first ethylenically unsaturated monomer in the presence of a transition metal chelate chain transfer agent, wherein said macromonomer comprises 20 to 100 wt%, based on the total weight of the macromonomer, of at least one α-methyl vinyl monomer, a vinyl monomer bearing no α-methyl group, or combinations thereof, provided that when a vinyl monomer bearing no α-methyl group is present, as polymerized units, in the macromonomer, the macromonomer must be terminated by a unit derived from an α-methyl vinyl monomer; forming an aqueous comb copolymer composition by a process comprising forming a polymerization reaction mixture by a process comprising combining said macromonomer aqueous emulsion with a monomer composition comprising at least one kind of ethylenically unsaturated monomer; polymerizing said polymerization reaction mixture in the presence of a free radical initiator;) forming a polymerization reaction mixture by a process comprising combining said macromonomer aqueous emulsion with a monomer composition comprising at least one kind of ethylenically unsaturated monomer; polymerizing said polymerization reaction mixture in the presence of a free radical initiator; isolation of the comb copolymer as a powder from said aqueous comb copolymer composition; (a) forming a solids blend comprising polyvinyl chloride and said powder of said comb copolymer; and (b) mixing and heating said solids blend to form said melt blend; (a) forming a solids blend comprising polyvinyl chloride and said powder of said comb copolymer; and (b) mixing and heating said solids blend to form said melt blend;