Synthesis and characterization of brush diblock and triblock copolymers bearing polynorbornene backbone and poly(l‐lactide) and/or poly(hexyl isocyanate) side chains by a combination of coordination and ring opening metathesis polymerization

Abstract

We report the synthesis of poly(l‐lactide) and poly(hexyl isocyanate) macromonomers using bischloro‐η5‐cyclopentadienyl(bicyclo[2.2.1]‐hept‐5‐en‐2‐oxy) Titanium (IV), [CpTiCl2(O‐NBE)]. These macromonomers bearing a norbornene end group were polymerized towards brush copolymers employing Grubbs' first generation catalyst. Brush copolymers consisting of blocks with different side chains were synthesized. The polymers were characterized by Size Exclusion Chromatography, Nuclear Magnetic Resonance, and their thermal properties were investigated by Thermogravimetric Analysis, and Differential Scanning Calorimetry analysis. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 3455–3465

Grubbs’ and Schrock’s Catalysts, Ring Opening Metathesis Polymerization and Molecular Brushes—Synthesis, Characterization, Properties and Applications

“…Thus, some researchers select only the exo-isomer, which exhibits less steric hindrance towards the complexation of the NBE double bond to the metal center. It has been reported by our team that in experiments with polylactide and poly(hexyl isocyanate) macromonomers with endo:exo = 75:25 NBE end groups and G1 catalyst, no significant amount of macromonomer was left unreacted (<1%) [ 50 ]. This small amount of “unreacted macromonomer” was attributed by researchers [ 34 , 50 ] to linear polymers not bearing NBE end units, rather than the steric hindrance of the endo macromonomers.…”

“…It has been reported by our team that in experiments with polylactide and poly(hexyl isocyanate) macromonomers with endo:exo = 75:25 NBE end groups and G1 catalyst, no significant amount of macromonomer was left unreacted (<1%) [ 50 ]. This small amount of “unreacted macromonomer” was attributed by researchers [ 34 , 50 ] to linear polymers not bearing NBE end units, rather than the steric hindrance of the endo macromonomers. The preparation of block molecular brushes with both macromonomers consisting of NBE endo:exo = 75:25 supports the latter hypothesis (~1% “macromonomer” did not react in the formation of the first block even after days of reaction and the addition of new amount of catalyst after those days).…”

“…The majority of the studies on lactide bottlebrushes involve PDLLA side chains (23 articles) [ 36 , 49 , 58 , 99 , 111 , 122 , 123 , 124 , 125 , 126 , 127 , 128 , 129 , 130 , 131 , 132 , 133 , 134 , 135 , 136 , 137 , 138 , 139 , 140 , 141 , 142 , 143 , 144 ]. There are only 10 articles with PLLA side chains [ 12 , 34 , 44 , 50 , 56 , 57 , 104 , 108 , 116 , 145 , 146 , 147 , 148 ] and one article where PDLA (and PLLA) side chains are used [ 145 ].…”

“…Block molecular brushes ( Figure 4 A) that have been reported in the literature are: (a) diblocks PS- b -PLLA [ 104 ], PS- b -PDLLA [ 111 ], PDLLA- b -P n BA [ 36 ], P3HT- b -PDLLA [ 143 ], PLLA- b -PHIC [ 50 ], PLLA- b -PCL [ 44 ] and (b) triblocks PLLA- b -PHIC- b -PLLA [ 50 ], PHIC- b -PLLA- b -PHIC [ 50 ], PEO- b -PDLLA- b -PBAEAM [ 57 ] and dumbbell shaped PDLLA 45 - b -PDLLA 15 - b -PDLLA 45 with PDLLA side chains of different MW [ 49 ]. Molecular brushes with random side chains ( Figure 4 B) have been synthesized: PLLA- co -PHIC [ 50 ], PLLA- co -PCL [ 44 ], PDLLA- co -P n BA [ 36 ], PDLLA- co -PDMS [ 138 ], P3HT-c o -PDLLA [ 139 , 143 ]. Bottlebrushes with two PLA chains per monomeric unit ( Figure 4 C) have been prepared [ 12 , 34 , 44 , 56 , 144 ].…”

Macromolecular Brushes Based on Poly(L-Lactide) and Poly(ε-Caprolactone) Single and Double Macromonomers via ROMP. Synthesis, Characterization and Thermal Properties

“…Other more complex structures, such as brushes on brushes have also been synthesized. The materials have been thoroughly characterized and their thermal properties have been investigated [38,39,40,41,42].…”