The blend properties of semi-crystalline and amorphous polycaprolactone (PCL) are shown here for the first time. The amorphous polycaprolactone (PCLB) having 20% branches was made by radical-ring-opening polymerization of 2-methylene-1,3-dioxepane. The presence of branches led to non-crystallinity in PCLB. The blends were made in solution in entire concentration range and showed some very interesting properties in terms of synergistic effect on crystallinity leading to the increased crystallinity of PCL and induced crystallinity of amorphous PCLB, minima in the % elongation and maxima in spherulite size depending upon the ratio of amorphous and crystalline part. There was a drastic increase in the compostability as compared to pure PCL on adding even low % of amorphous PCLB in the blends without affecting the thermal stability. The addition of PCLB also affected the transparency and it increased exponentially from about 8% at 650 nm for PCL to about 45% for a blend with composition PCL:PCLB 30:70. (C) 2010 Elsevier Ltd. All rights reserved.