kinetic chain length and degree of polymerization

The number average degree of polymerization is equal to the ratio of velocity of propagation to that of termination of the polymer chain, i.e. This information can tell us how long it will take for a polymer to reach an optimum length. The expression for kinetic chain length is = 2 2 2 = 0.0138 × 6.532 2 × (2.0 × 10−4) = 1471 51. VI.Kinetic Chain Length VII.Chain-Transfer Reactions A. Describe the kinetics of the main features of free radical chain polymerization (initiation, propagation, termination and chain transfer). the number average molecular weight (M n) is a linear function of monomer conversion. 2009, 131, 7960-7961, the limited degree of polymerization (DPn ~ 10) obtained by traditional azobisisobutyronitrile (AIBM)-initiatedrradical polymerization of the cyclic diene_3^__ methylenecyclopentene was mentioned. Polycondensation Kinetics of Lactic Acid Degree of polymerization (DP) is one of the most important structural properties of cellulose. In fact the kinetic chain length is one factor which influences the average degree of polymerization, but there are other factors as described below. It is given by the ratio of the rate of polymerization to the rate of initiation and under steady-state conditions where Rt = Ri: (8-58) v = R p R i = k p [ M] [ M •] 2 f k d [ I] = k p [ M] [ M •] 2 k t [ M •] 2 Other graphs of bounded expansion include . The kinetic chain length expression given by, v=( k p 2 /2k t)([M] 2 /R p) is applicable to all cases of termination, irrespective of the mechanism involved. • To emphasize the importance of stabilization of the charged reactive center on the growing chain. Transfer to Solvent VIII.Temperature Dependence of Degree of Polymerization IX.Ionic and Coordination Chain Polymerization A.Nonradical Chain Polymerization B.Cationic Polymerization 1. 3.2: Kinetics of Step-Growth Polymerization. For a solution of 0.01 M peroxide and 1.0 M styrene in benzene, the initial rates of initiation and polymerization are 4.0 x 10" mol/(L•sec) and 1.5 x 10-7 . Derive the rate of polymerization and kinetic chain length . Monomer transfer. for polymerization, with reference to free radical polymerization as the most common route to high polymer. If one assumes that the kinetic rate constant Take my course now at https://www.geekgrowth.com. What is the value of chain length, when monomer concentration is 6.53 mol/l and rate of polymerization is 2.0×10-4 mol/l-s? • To develop expressions for the average degree of polymerization and molecular weight distribution for anionic polymerization. Which of the following equations is the correct expression for the number average degree of polymerization when chain transfer occurs in a free radical synthesis A. In the absence of any side reactions, kinetic chain length is related directly to degree of polymerization depending on the mode of termination. The kinetic chain length v is the average number of monomers that react with an active center from its formation until it is terminated. Polymerization technique where unsaturated monomer molecules add onto the active site on a growing polymer chain one at a time. In the present work, the simple reaction mechanism of poly-condensation of a bifunctional monomer with equal reactivity of the functional groups was used. 1 2.3 NC N CN bulk, 20 h, 80 °C (a) Provide the electroir-afKW-pushing mechanistic steps for initiation and propagation . The kinetic chain length and therefore the degree of polymerization can influence certain physical properties of the polymer, including chain mobility, glass-transition temperature, and modulus of elasticity . There are a limited number of these active sites at any moment during the . Kinetic chain length. It can also provide insight into how the polymerization occurs, just as kinetics can provide insight . It is analogous to the degree of polymeri­ zation in addition polymerization. [T] [M] x n = x o + C C. [M] [T] C x 1 1 n . c) Coupling radicals in a preferred termination step in free-radical mechanism is NOT possible. The number average degree of polymerization is equal to the ratio of velocity of propagation to that of termination of the polymer chain, i.e. 10. Problem KP3.4. Transcribed image text: If termination is by disproportionation, the kinetic chain length is equal to the number average degree of polymerization b) Free-radical polymerization is the same as step-growth polymerization. Show how the use of the steady-state assumption allows the derivation of equations describing the rate of polymerization, conversion, the kinetic chain length and the effect of chain transfer. In polymer chemistry, polymerization is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. Polymerization is possible only if ∆G < 0 for the Thus, varying initiator concentration can control molecular weight. M is the molecular weight of the polymer, DP is the degree of polymerization and the M 0 is the formula weight of the repeating unit. (Rp)A(a), where n̄0 is the kinetic chain length of the polymer formed by transfer and A (a) is unity (predominance of transfer) and 1/(1-2a) (no transfer). This is reasonable because increasing the number of growing chains increases the probability of termination. Thus, varying initiator concentration can control molecular weight. The final length of a polymer chain will depend on side reactions (chain-transfer) and the type of termination This is reasonable because increasing the number of growing chains increases the probability of termination. Redox transfer. FEATURE 2 Pre-determinable degree of polymerization: (DP n), i.e. Mechanism 2. By analogy to radical polymerization, the kinetic chain length in cationic polymerization can be expressed as the ratio of propagation rate to initiation rate. The kinetic chain length ν is defined as the average number of monomer units added to a chain per effective radical. The kinetic chain length represents the average number of monomer molecules in a polymer molecule. Wikipedia. Ex: calculate the degree of polymerization of a sample of . the average polymerization degree of reactor content, the average residence time, and the reactor volume in the case of continuous flow operation/ random scissioncan be derived.They are shown byEqs. MCQs: The bimolecular biradical mechanism in spontaneous thermal polymerization is very appreciated for its successful attempts to induce polymerization by biradicals formed. 1.4 KINETIC CHAIN LENGTH AND THE DEGREES OF POLYMERIZATION The average number of monomers reacting with a given active center from its initiations to its termination is represented by ν, that is kinetic chain length. Chain Transfer! M= (DP) M0. The degree of polymerization decreases with increases of temperature and of initiator concentration and with decrease of monomer concentration. The number average degree of polymerization Xn for polymers made by free radical polymerization can also be predicted from the kinetics. In step-growth polymerization, in order to achieve a high degree of polymerization and hence molecular weight, X n, a high fractional monomer conversion, p, is required, according to Carothers equation X ¯ n = 1 − p {\displaystyle {\bar {X}}_{n}={\frac {1}{1-p}}} For example, a monomer conversion of p = 99% would be required to achieve X n = 100. However it often differs from the kinetic chain length for several reasons: 1.4 KINETIC CHAIN LENGTH AND THE DEGREES OF POLYMERIZATION The average number of monomers reacting with a given active center from its initiations to its termination is represented by n, that is kinetic chain length. Kinetic Chain Length, Degree of Polymerization, and Chain Transfer . A method has been developed for the determination of the heat of the acts of chain growth qg and of the summary heats of the acts of chain initiation and termination q** for the radical polymerization of vinyl monomers at the conditions of moderately short kinetic chains, when the length of the kinetic chain v < 100, but the degree of polymerization is ¯P > 20. Contents 1 Calculating chain length 2 Kinetic chain length and degree of polymerization 2.1 Termination by disproportionation 4. 100 chains are started 2. What is polymerisation reaction? Aside theory, the course also focus on calculations and predictions of important parameters and outcomes of polymerizations, including the degree of polymerization, average molecular weight, average functionality, gel point, kinetic chain length, rate constants, chain transfer, copolymerization composition etc. A. Explanation: The number average degree of polymerization is related to kinetic chain length, when termination occurs simultaneously by combination and disproportionation, by the following expression-Xn = [2(y+1)/(y+2)]v = 686. The word kinetic is added to chain length in order to distinguish the number of reaction steps in the kinetic chain from the number of monomers in the final macromolecule, a quantity named the degree of polymerization. The degree of polymerization can be calculated by using the following relationship if a molecular weight of a polymer molecule is known. The number average degree of polymerization Xn for polymers made by free radical polymerization can also be predicted from the kinetics. A procedure is developed that allows the calculation of chain length distributions of polymers prepared by periodic modulation of the initiation process, considering termination by disproportionation and chain transfer. For the case of a (pseudostationary) laserpulse initiated polymerization process a closed solution can be derived for the chain length distribution (cld) of dead polymer and . Under steady state conditions, this is simply the p _ Vpropagation Soc. [9] However it often differs from the kinetic chain length for several reasons: chain termination may occur wholly or partly by recombination of two chain radicals, which doubles the degree of . The kinetic chain length ν is defined as the average number of monomer units added to a chain per effective radical. The degree of polymerization or chain length is then 1000 by the first (IUPAC) definition, but 500 by the second. Both become the actual kinetic chain length when transfer is absent. if initiator, by using a kinetic-chain transfer agent etc. Determining chain length in free radical polymerization.Let me teach you more! " Kinetic chain length and molecular weight! Average number of units called monomers added to a growing chain during chain-growth polymerization. the number of monomeric units polymerized for each molecule originally activated, and the degree of polymerization will enable transfer reaction to be detected, for in such a case the chain length will be greater than the degree of polymerization. 1. - (A) True - (B) False kinetic chain length ℇ and DP0.The kinetic chain length is the number of The general relationship between the degree of polymerization (Xn) and the kinetic chain length (n) and the fraction of propagating chains (a) are Xn= 2n/(2-a) why do alkyl groups favor cationic polymerization . Kinetics of Step-Growth Polymerization. Catalytic chain transfer (CCT) Instantaneous chain length distribution (CLD) and chain transfer By analogy to radical polymerization, the kinetic chain length in cationic polymerization can be expressed as the ratio of propagation rate to initiation rate. In order to derive kinetic equations for these reactions certain approximations are made. The second form of the equation is valid at steady-state . Kinetic chain length is defined as the average number of monomers that react with an active center such as a radical from initiation to termination. It is important to understand how reactions proceed over time. Autoacceleration. Under steady state conditions, this is simply the 1.4 KINETIC CHAIN LENGTH AND THE DEGREES OF POLYMERIZATION The average number of monomers reacting with a given active center from its initiations to its termination is represented by ν, that is kinetic chain length. At the beginning of the reaction, long chains are formed and longer reaction times have little effect on the average molecular weight it only increases the polymer yield. The general DP equation . Addition-fragmentation chain transfer (AFCT) Polymer transfer. Assuming no chain transfer effect occurs in the reaction, the number average degree of polymerization P n can be correlated with the kinetic chain length. And the chain length is given by-v =( k p 2 /2k t) ([M] 2 /R p) So, for pure thermal polymerization, the expression for kinetic chain length is given by, v = k p /2(k i k t) 0.5. [] [] [] νν νν == = ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ = ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ • R R or R R k k M M and k k M R p i p t p t p . Step-growth and chain-growth polymerization . Transfer to Undiluted Monomer B. Q: What is the degree of polymerization for polyvinyl chloride, having kinetic chain length as 400 and terminated by coupling mechanism? Mechanism 2. [] [] [] νν νν == = ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ = ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ • R R or R R k k M M and k k M R p i p t p t p . The kinetic chain length is related to the number-average degree of polymerization (DP), which is the average number of monomers consumed per polymer chain formed. 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