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Replacing petroleum-based plastics with alternatives that are degradable and synthesized from annually renewable feedstocks is a critical goal for the polymer industry. Achieving this goal requires the development of sustainable analogs to commodity plastics which have equivalent or superior properties (e.g. mechanical, thermal, optical etc.) compared to their petroleum-based counterparts. This work focuses on improving and modulating the properties of a specific sustainable polymer, poly(lactide) (PLA), by incorporating it into triblock and multiblock copolymer architectures. The multiblock copolymers in this work are synthesized directly from dihydroxy-terminated triblock copolymers by a simple step-growth approach: the triblock copolymer serves as a macromonomer and addition of stoichiometric quantities of either an acid chloride or diisocyanate results in a multiblock copolymer. This work shows that over wide range of compositions, PLA-based multiblock copolymers have superior mechanical properties compared to triblock copolymers with equivalent chemical compositions and morphologies. The connectivity of the blocks within the multiblock copolymers has other interesting consequences on properties. For example, when crystallizable poly(l-lactide)-based triblock and multiblock copolymers are investigated, it is found that the multiblock copolymers have much slower crystallization kinetics. Additionally, the total number of blocks connected together is found to eect the linear viscoelastic properties as well as the alignment of lamellar domains under uniaxial extension. Finally, the synthesis and characterization of pressure-sensitive adhesives based upon renewable PLA-containing triblock copolymers and a renewable tackifier is detailed. Together, the results give insight into the effect of chain architecture, composition, and morphology on the mechanical behavior, thermal properties, and rheological properties of PLA-based materials.

Monobrominated diblock copolymers composed of poly(styrene) (PSt), poly(methylacrylate) (PMA), or poly(methyl methacrylate) (PMMA) were synthesized by consecutive atom transfer radical polymerizations (ATRP). The brominated diblocks were utilized in atom transfer radical coupling (ATRC) and radical trap-assisted ATRC (RTA-ATRC) reactions to form ABA type triblock copolymers. Once PMMA-PStBr and PSt-PMABrBr were produced by ATRP, the synthes of PSt-PMA-PSt and PMMA-PSt- PMMA by ATRC and also by RTA-ATRC were attempted. The coupling methods were compared and it was found that RTA-ATRC succeeded in synthesizing PSt-PMA-PSt where ATRC could not, and that RTA-ATRC improved coupling over ATRC for PMMAPSt- PMMA. Incorporation of the radical trap 2-methyl-2-nitrosopropane (MNP) midchain allowed for simple thermal cleavage of the triblock to confirm the RTA-ATRC pathway occurred in preference over the head to head radical coupling pathway of ATRC. Triblocks made by ATRC did not cleave under our conditions, as no MNP was present and thus no labile C-O bond was incorporated. The RTA-ATRC pathway allowed for lower catalyst amounts (2 molar equivalents of copper(I)bromide and 2 molar equivalents of copper metal) and a high degree of coupling at lower temperatures (40°C). The RTA-ATRC improved upon ATRC because of its ability to generate a persistent radical and proceed by first order kinetics with respect to the chain end radical.

Due to their ability to straddle phase boundaries, polymer brushes represent a model system for studies of polymer-modified surfaces. The research presented in this dissertation focuses on understanding a special type of polymer brushes formed at the solid-fluid interface by self-assembly of block copolymer chains that have the ability to tether by multiple ends, thus creating loops on the surface. Specifically, I study the self-assembly of a series of poly(2-vinylpyridine)-polystyrene-poly(2-vinylpyridine) (PVP-b-PS-b-PVP) triblock copolymers and PVP-b-PS star block copolymers adsorbed from the selective solvent toluene onto silicon and mica surfaces. The triblock and star copolymers have different molecular weights and PS/PVP ratios systematically varying from asymmetric to symmetric compositions. In the case of the stars, the number of arms is also varied. The self-assembly processes and structure are studied mostly in a solvent that is selective for the PS block. I focus on understanding how having multiple tethering points and how composition parameters (molecular weight, PS/PVP ratios, and number of arms) affect the kinetics of preferential adsorption and layer structure of the resulting brushes. The triblock copolymers form a looped polymer layer with average properties that can be described by considering the brush as made of equivalent diblocks of half the molecular weight of the triblock copolymer. The kinetics of preferential adsorption displays the two regimes expected for adsorption of diblock copolymers - there is rapid adsorption at early times followed by a transition to a slower regime. However, there are characteristic differences for the triblock materials: they adsorb faster than an analogous diblock copolymer of similar (total) molecular weight, and form a brush with approximately one-half the thickness of the brush made from the analogous diblock copolymer. Both characteristics are a direct result of the looped conformation adopted by the preferentially adsorbed triblocks, and this looping also results in the structure that displays a polydispersity-like effect introduced by the layer having a distribution of distances between tethering points of the brush chains. The kinetics of preferential adsorption and the force profiles for the adsorbed star copolymers are shown to be affected by star parameters such as total molecular weight, PS/PVP ratio, and number of arms. However, the dependence on these parameters is more complex in this case and there is no obvious trend evident in the data. The results reported in this dissertation show that by manipulating copolymer architecture, looped polymer brushes can be created, and their layer structure, interactions, and therefore properties, can be manipulated by chain parameters such as: molecular weight, asymmetry of chains, and degree of branching. Also, the detailed knowledge of the kinetics of preferential adsorption presented in this dissertation opens the possibility of manipulating brush structure by controlling, for example, chain grafting densities or creating mixed polymer brushes.