Microwave‐assisted ring‐opening polymerization of ϵ‐caprolactone

Liao, Liqiong; Liu, L. J.; Zhang, C.; He, Feng; Zhuo, Ren‐Xi; Wan, Kun

doi:10.1002/pola.10256

Cited by 84 publications

(69 citation statements)

References 19 publications

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“…This also does not impose any limitation on the upper limit on the usage of the catalyst loading because it can be separated. However, the method of synthesizing PCL by ROP using zinc is fairly new (apart from a recent study demonstrating the use of zinc as a catalyst for PCL synthesis 39 ) and results of kinetic investigations with continuous distribution kinetics are presented here.…”

Section: Introductionmentioning

confidence: 98%

“…38 Recently, microwave-assisted ROP of ⑀-caprolactone has been reported. 39 Zinc is an oligoelement, which can be present in the human body at a level of 1.36 -2.32 g. 40 In this aspect, even if zinc residue is left in the polymeric material, it can be conveniently applied for biomedical applications. 23 The zinc-aided polymerization is purely catalytic and heterogeneous and thus the downstream processing for the separation of zinc from polymer is relatively easy.…”

Section: Introductionmentioning

confidence: 99%

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Kinetics of microwave‐assisted polymerization of ϵ‐caprolactone

Sivalingam

Agarwal

Madras

2003

J of Applied Polymer Sci

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ABSTRACT:The kinetics of polymerization of ⑀-caprolactone (CL) in bulk was studied by irradiating with microwave of 350 W and frequency of 2.45 GHz with different cycle-heating periods (30 -50 s). The molecular weight distributions were determined as a function of reaction time by gel permeation chromatography. Because the temperature of the system continuously varied with reaction time, a model based on continuous distribution kinetics with time/temperature-dependent rate coefficients was proposed. To quantify the effect of microwave on polymerization, experiments were conducted under thermal heating. The polymerization was also investigated with thermal and microwave heating in the presence of zinc catalyst. The activation energies determined from temperature-dependent rate coefficients for pure thermal heating, thermally aided catalytic polymerization, and microwave-aided catalytic polymerization were 24.3, 13.4, and 5.7 kcal/mol, respectively. This indicates that microwaves increase the polymerization rate by lowering the activation energy.

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Kinetics of microwave‐assisted polymerization of ϵ‐caprolactone

Sivalingam

Agarwal

Madras

2003

J of Applied Polymer Sci

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“…Although many efforts have been made to catalyze the process, it still takes over 10 h or several days to get the polymerization completed. Liao et al 44 attempted the microwave-assisted ring-opening polymerization of ε-caprolactone in sealed ampoules. Using 0.1% (mol/mol) stannous octanoate as catalyst, they synthesized the polymer at 180°C in 30 min.…”

Section: Polymersmentioning

confidence: 99%

Microwave-assisted wet chemical synthesis: advantages, significance, and steps to industrialization

Shi¹,

Hwang²

2003

JMMCE

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Previous research has revealed several advantages from microwave-assisted wet chemical synthesis in reaction acceleration, yield improvement, enhanced physicochemical properties and the evolvement of new material phases. The study present examples that demonstrate the significance of these advantages to industrial application. In order to achieve successful industrial application there is a need to distinguish between the microwave athermal (not excited by heat) effect from the microwave-induced thermal effect (temperature rise). The optimization of this new process has to be systematically investigated, so the advantages and benefits of this new technology can be fully exploited. Advantages and significance ?-Fe 2 O 3 based magnetic materials?-Fe 2 O 3 based magnetic materials have been extensively used as recording materials because of their good magnetic properties. The emergence of nanomagnetic technology has imposed new demands upon magnetic materials. To fabricate ultrahigh density and ultrahigh speed data storage devices, which work on the magnetic -spintronic concept, magnetic materials with nanoscale particles are highly preferred 1 . Conventionally, ? -Fe 2 O 3 powders with monodispersed particles are synthesized first by means of forced hydrolysis of ferric nitrate or ferric chloride in aqueous solutions, which produces α-Fe 2 O 3 , and then the α-Fe 2 O 3 are transformed into ?-Fe 2 O 3 in a high-temperature process 2,3 . To effectively control the particle shape and particle size, which are essential for achieving the desired magnetic properties, the hydrolysis solution must be very dilute. For producing micron-and submicron-sized particles, the concentrations of the ferric irons are generally within a range around 0.02M 2, 4, 5 and for producing nanosized powders, the ferric concentration should be much lower. In addition to dilute solutions, the conventional hydrolysis has to be carefully controlled and it generally requires 2-7 days. This means that, even based upon the shortest processing time and highest concentration, the rate for producing the nanosized iron oxide powders would be less than 0.014 gram per liter per hour. In order to use nanosized magnetic materials for industrial applications, appreciable acceleration of the process and an increase in the ferric concentration are required.Several researchers have attempted the iron oxide synthesis via microwave-assisted hydrolysis. Komarneni et al demonstrated that under otherwise identical processing conditions, synthesis of crystalline hematite by a microwave-hydrothermal approach was 36 times faster than by conventional hydrothermal methods 6 . Our study shows the capability of controlling the particle shape and particle size with this rapid synthesis approach. Rigneau et al further shortened the processing time to 30 minutes and also increased the ferric concentration to 0.05M 7 , which could increase the production rate over one hundred times. The even more striking finding from their results was that the microwave synthesized Fe 2 O 3 p...

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“…20,21 Polymerization reactions also can be significantly improved by microwave irradiation, and the microwave-assisted syntheses of biodegradable polymers have proved to be successful. [22][23][24][25][26][27][28][29] Our group has previously reported the microwave-assisted ROP (MROP) of cyclic esters such as "-caprlactone 30,31 and lactides, 32 and the corresponding polyesters have been successfully synthesized using this method.…”

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confidence: 99%