In stepwise polymerization, the addition of a small amount of catalyst results into :
Reduction in time required for reaching high degree of polymerization
In step-growth (stepwise) polymerization the degree of polymerization is set by the extent of reaction p through the Carothers equation \(\bar{X}_{n} = \frac{1}{1-p}\); high polymer is obtained only at p very close to 1.
For an externally catalysed polyesterification the kinetics are second order and \(\frac{1}{1-p} = 1 + k'[M]_{0}t\), so \(\bar{X}_{n}\) grows linearly with time with slope \(k'[M]_{0}\).
Adding a catalyst increases the rate constant \(k'\), so a given extent of reaction, and therefore a high degree of polymerization, is reached in a shorter time.
A catalyst speeds up the esterification rather than lowering it, and it does not lengthen the reaction time. The molecular weight distribution at a given conversion is governed by p alone, so the distinctive effect of the catalyst is kinetic: it shortens the time needed.
Therefore the catalyst reduces the time required for reaching a high degree of polymerization.
Hence, Reduction in time required for reaching high degree of polymerization.
Important Questions from Mixed Topic (MH-SET)
.................... is a client server application that identifies each host on the internet with a unique user-friendly name.
Every OS has a ................ or .......... which primarily resides in the main memory of the computer to perform some of the basic functions of the OS.
(i) Kernel
(ii) Interface
(iii) Nucleus
(iv) Compiler
Codes:
Which of the following are referred to as low level language?
(i) Machine language
(ii) Assembly language
(iii) High level language
(iv) Natural language
Codes:
Match the following:
List I List II (a) New York Public Library (i) Shelv AR (b) Miami University Augmented Research Group (ii) Smart library (c) Oula University Library (iii) Wolf Walk (d) North Carolina State University (iv) Find the future Codes:
Which part of the QR code represents the encoded data?
