controlled ring-opening polymerization: polymers with ... 8664/fulltext01.pdf · controlled...

Download Controlled Ring-Opening Polymerization: Polymers with ... 8664/FULLTEXT01.pdf · Controlled Ring-Opening…

Post on 20-Jun-2018

212 views

Category:

Documents

0 download

Embed Size (px)

TRANSCRIPT

  • Controlled Ring-Opening Polymerization:

    Polymers with designed

    Macromolecular Architecture

    Kajsa M. Stridsberg

    Department of Polymer TechnologyRoyal Institute of Technology

    Stockholm, Sweden2000

    Akademisk avhandlingsom med tillstnd av Kungliga Tekniska Hgskolan framlgges till offentliggranskning fr avlggande av teknisk doktorsexamen fredagen den 3 mars 2000,kl. 10.00 i Kollegiesalen, Administrationsbyggnaden, Valhallavgen 79, KTH,Stockholm. Avhandlingen frsvaras p engelska.

  • ISBN 91-7170-522-8

    Printed by Kista Snabbtryck AB, Stockholm, Sweden

  • Controlled Ring-Opening Polymerization:Polymers with designed Macromolecular Architecture

    Kajsa M. Stridsberg

    ABSTRACTThis thesis summarizes the development of new catalyst systems for ring-openingpolymerization and their use in the production of macromolecules with advanced architecture.

    The influences of reaction conditions, i.e. reaction temperature, solvent and reaction time,on the polymerization kinetics have been evaluated for the ring-opening polymerization (ROP)of 1,5-dioxepan-2-one (DXO) initiated by a cyclic tin-alkoxide. The purpose has been toachieve a controlled ring-opening polymerization of lactones and lactides, resulting in polymerswith desirable properties. The mechanism and kinetics of controlled ring-openingpolymerization of L-lactide (L-LA) have been investigated, leading to hydroxy telechelicpolymers to be used in macromer reactions of various natures.

    The ROP mechanism of DXO with stannous octoate as catalyst has been investigatedtheoretically with hybrid density functional methods. A new mechanism has been proposedwhich provides an explanation of the experimental observations. The ROP mechanism hasbeen shown to involve the formation of a tin-alkoxide complex, which subsequentlycoordinates a monomer. It has been demonstrated that the ring-opening of the monomerproceeds via a concerted four-center transition state.

    Elastomeric tri-block copolymers have been obtained from L-LA and DXO with adifunctional tin-initiator. A two-step process has been developed to achieve a well-defined tri-block copolymer, poly(L-lactide-b-1,5-dioxepan-2-one-b-L-lactide) (poly(L-LA-b-DXO-b-L-LA)), in good yield. Thermal analysis of the poly(L-LA-b-DXO-b-L-LA) has been used toexamine the morphology of the block copolymer. The crystallinity and melting temperaturehave been shown to increase with increasing amount of L-LA in the copolymer, but the glasstransition temperature was only slightly influenced by the polymer composition.

    Poly(L-LA-b-DXO-b-L-LA) has been subjected to hydrolytic degradation in phosphatebuffer solution. The influence of molecular weight and chemical composition on thehydrolysability has been investigated. The molecular weight change, weight loss andcomposition changes have been characterized in order to determine the degradation pathway.The degradation of poly(L-LA-b-DXO-b-L-LA) was characterized by a significant decrease inmolecular weight immediately after immersion in the buffer solution and a progressive increasethe amount of L-LA in the remaining copolymer with increasing degradation time. The primarydegradation products formed during hydrolysis have been detected as lactic acid and 3-(2-hydroxyethyl)-propanoic acid. Results indicate that the composition had no effect on the rate ofdegradation. The major factor determining the degradation rate was the original molecularweight.

    Keywords: controlled ring-opening polymerization, poly(1,5-dioxepan-2-one), poly(L-lactide),kinetics, mechanism, block copolymerization, poly(L-lactide-b-1,5-dioxepan-2-one-b-L-lactide), characterization, hydrolytic degradation,

  • LIST OF ARTICLES

    This thesis is a summary of the following papers:

    I. Ring-Opening Polymerization of 1,5-Dioxepan-2-one Initiated by a CyclicTin-Alkoxide Initiator in Different Solvents. K. Stridsberg, A.-C.Albertsson, Journal of Polymer Science: Part A: Polymer Chemistry 1999,37, 3407

    II. Di-hydroxy Terminated Poly(L-lactide) obtained by Controlled Ring-Opening Polymerization: Investigation of the Polymerization Mechanism,K. Stridsberg, M. Ryner, A.-C. Albertsson, Macromolecules, accepted forpublication

    III. Controlled Ring-Opening Polymerization of L-lactide and 1,5-dioxepan-2-one forming a Tri-Block Copolymer, K. Stridsberg, A.-C. Albertsson,submitted to Journal of Polymer Science: Part A: Polymer Chemistry

    IV. Changes in Chemical and Thermal Properties of the Tri-Block CopolymerPoly(L-lactide-b-1,5-dioxepan-2-one-b-L-lactide) during HydrolyticDegradation, K. Stridsberg, A.-C. Albertsson, Polymer, accepted forpublication

    It also contains parts of the following article:

    V. The Mechanism of Ring-Opening Polymerization of Lactones and Lactideswith Stannous(II) 2-ethylhexanoate as Catalyst studied with HybridDensity Functional Methods, K. Stridsberg, M. Ryner, A.-C. Albertsson, H.von Schenck, M. Svensson, submitted to Macromolecules

  • TABLE OF CONTENTS1 PURPOSE OF THE STUDY ............................................................ 1

    2 INTRODUCTION............................................................................. 3

    2.1 Background.................................................................................................... 32.2 Ring-opening polymerization of cyclic esters ............................................... 4

    2.2.1 Cationic ring-opening polymerization .................................................... 52.2.2 Anionic ring-opening polymerization ..................................................... 52.2.3 Coordination-insertion ring-opening polymerization.......................... 6

    2.3 Organometallic compounds as initiators for the ROP of lactones andlactides....................................................................................................................... 7

    2.3.1 Stannous(II) 2-ethylhexanoate ............................................................... 92.3.2 Aluminum tri-isopropoxide ................................................................... 102.3.3 Tin-alkoxides ......................................................................................... 112.3.4 Lanthanide alkoxides............................................................................ 12

    2.4 Macromolecular architecture ...................................................................... 122.4.1 Homopolymers ....................................................................................... 122.4.2 Block copolymers ................................................................................... 132.4.3 Star-shaped (co)polymers...................................................................... 14

    2.5 Biodegradable polymers.............................................................................. 152.5.1 Polymer degradation ............................................................................. 152.5.2 Polyglycolide and copolymers ............................................................... 162.5.3 Polylactide and copolymers................................................................... 162.5.4 Poly(-caprolactone) and copolymers .................................................... 18

    3 SYNTHESIS ................................................................................... 19

    3.1 Materials...................................................................................................... 193.2 Initiator........................................................................................................ 19

    3.2.1 1,1,6,6-tetra-n-butyl-1,6-distanna-2,5,7,10-tetraoxacyclodecane........ 193.3 Monomers .................................................................................................... 20

    3.3.1 L-lactide ................................................................................................. 203.3.2 1,5-dioxepan-2-one................................................................................. 20

    3.4 Polymerization............................................................................................. 213.4.1 Homopolymerization of DXO and L-lactide ......................................... 213.4.2 Block copolymerization of 1,5-dioxepan-2-one and L-lactide .............. 21

  • 4 CHARACTERIZATION ................................................................. 23

    4.1 Hydrolytic Degradation............................................................................... 234.1.1 Sample Preparation............................................................................... 234.1.2 In vitro degradation of the poly(L-lactide-b-1,5-dioxepan-2-one-b-L-lactide) tri-block copolymers. ............................................................................ 23

    4.2 Instrumental Analysis................................................................................. 244.2.1 Mass Spectroscopy (MS) ........................................................................ 244.2.2 Nuclear Magnetic Resonance Spectroscopy (NMR) ............................. 244.2.3 Size Exclusion Chromatography (SEC) ................................................ 254.2.4 Differential Scanning Calorimetry (DSC) ............................................ 254.2.5 Solid Phase Extraction (SPE)................................................................ 264.2.6 Gas Chromatography Mass Spectroscopy (GC-MS) .......................... 264.2.7 X-ray Diffraction Pattern Analysis ....................................................... 26

    5 RESULTS AND DISCUSSION ..................................................... 27

    5.1 Influence of reaction conditions on the homo-polymerization of 1,5-dioxepan-2-one and L-lactide .............................................................................

Recommended

View more >